2. Sonic journeying and acoustic intimacy

Chris Watson’s El Tren Fantasma (2011) provides a particularly generative point of comparison for Bayu Nokturnal II, not only for its immersive narrative construction but also for how it exemplifies what LaBelle (Reference LaBelle2010) terms acoustic intimacy, a sonic condition where the environment is not merely represented, but sensorially inhabited. Watson’s work assembles field recordings of a defunct Mexican railway into a cinematic sequence of spatial, temporal and cultural vignettes. His compositional choices – strategic layering, dynamic contrast and sudden silences – activate a listening body that moves through space as much as sound. Similarly, Bayu Nokturnal II invites the listener to traverse the subterranean acoustics of Gua Tempurung through a dramaturgy of spatialised textures, filtered frequencies and sonic metaphors rooted in corporeality. This connection is especially felt in the act of walking through Gua Tempurung, an embodied journey captured through reverberant footfalls, filtered echoes and dripping water trails that chart a path from the cave’s wind tunnel entrance to the Golden Flowstone chamber. As in El Tren Fantasma, where the train acts as both vehicle and narrative device, the cave here functions as a resonant chamber of memory and meaning. The listener is not just presented with sonic events, but implicated in the act of passage; what Watson’s work achieves through rail travel, Bayu Nokturnal II replicates through the bodily navigation of echoic voids.

Crucially, the cave is not only rendered as a sound object but as an acoustic territory (LaBelle, Reference LaBelle2010, 1–23), a site where physical space, cultural trace and inner resonance converge. Through techniques such as spectral filtering, spatial manipulation, resonance tuning (e.g., matching frequencies to human head-neck cavities) and subtle post-processing methods, the composition evokes a form of listening-with-the-body, transforming environmental sound into a medium of spatial, emotional and mnemonic connection. The layering of processed sonic cells onto multitrack arrangements results in a quasi-site-specific soundscape that respects the temporal and spatial gestures of the original acoustic environment. The slow evolution of textures and proportionally recurring motifs mirrors Watson’s approach of maintaining the temporal flow of lived environments while guiding the listener through an emotional and sensory journey. These techniques are aligned with principles in soundscape composition, where site-specificity is preserved not only through unaltered sounds but also through contextual association and compositional intention (Truax, Reference Truax2001, 1–3; Westerkamp Reference Westerkamp2002, 49–53). Additionally, the spectral modulations and extended time-based transformations reflect electroacoustic approaches often used in acousmatic music to evoke introspection and awareness (Smalley Reference Smalley1997, 110–112). The intention behind these strategies is to elicit a heightened sense of aural perception and psychological stillness – what LaBelle (Reference LaBelle2010, 45–47) refers to as acoustic dwelling, a sonic immersion that fosters spatial belonging and emotional anchoring. In this regard, Bayu Nokturnal II, following the foundational design of Seed of Life 4: Rest and Shelter, operates as an aural meditation, reconstructing Gua Tempurung not only as a geographical entity but as an imagined auditory sanctuary where listeners can locate calm, memory and meaning.

While El Tren Fantasma captures the spectral memory of industrial transit – its metallic inertia, rhythmic momentum and political history of erasure – Bayu Nokturnal II counters with an inward, pre-industrial temporality, where time feels suspended rather than accelerated. Watson’s train line is a path of disappearance, a relic of modernity’s failed promise, while the Gua Tempurung cave represents continuity: an ancient site of shelter, ritual and resonance, echoing with traces of a human presence that predates writing or machinery. Watson foregrounds the train as a mechanical protagonist – a moving apparatus that frames all sonic events within its motion. In contrast, Bayu Nokturnal II avoids a singular narrative agent, instead drawing attention to bodily perception itself. The sonic subject here is not the machine but the listener’s own sensate body – hearing through the cave’s chambers, breathing in the reverberant silence and feeling frequencies resonate through cranial and thoracic cavities. Where Watson moves the listener across external terrains, Bayu Nokturnal II turns inward, cultivating a type of stationary motion: the listener dwells in place, immersed in the spectral remains of geophonic and biophonic activity.

This inversion reframes LaBelle’s notion of acoustic intimacy. In Watson’s work, intimacy arises through historical immersion – being sonically surrounded by a now-absent world. In Bayu Nokturnal II, intimacy is constructed through psychoacoustic proximity: subtle drones, filtered rain echoes and human-anatomy-tuned resonances create an internal space where sound merges with breath, memory and bone. Thus, the counterpoint is not merely thematic or procedural, but ontological: one composition maps lost infrastructures; the other animates primordial enclosures. Together, they reveal contrasting yet complementary strategies for composing with place – not just as setting, but as agentive, resonant and embodied territory. In this way, Watson’s work becomes not only a reference but a conceptual counterpoint – while El Tren Fantasma records the hauntology of industrial modernity, Bayu Nokturnal II reimagines prehistoric resonance through an intimate, tactile ecology of listening.

3. Gua Tempurung and the sonic fingerprint of place

Gua Tempurung, one of the largest limestone cave systems in Peninsular Malaysia, serves not only as a geological marvel but also as a profound acoustic reservoir. Geologically, the cave belongs to the Kinta Limestone formation and is believed to have formed during the Paleozoic era over 250 million years ago (Tan Reference Tan2019, 126–147). Historically, it has served as a shelter for indigenous Orang Asli communities and later as a hideout for communist insurgents during the Malayan Emergency (1950s) (Gokayu 2024; Penang Insider 2021). These layered histories inform the sonic characteristics I sought to capture – echoes of deep time, sedimented memory and cultural residue. My fieldwork at Gua Tempurung involved navigating its chambers with a portable Zoom H6 recorder equipped with an XYH-6 stereo capsule. This configuration employs an X-Y coincident microphone pair angled at 120 degrees, enabling high-fidelity stereo spatial imaging, a technique suitable for ambient and environmental sound capture (Ricour Reference Ricour2017, 37). The constraints of minimal lighting, unpredictable cave humidity and safety considerations imposed certain recording limitations. Yet, these very conditions also contributed to the unique sonic fingerprint of the space. The biophony of intermittent bat calls, dripping water and the soft crunch of footsteps against damp stone merged with the cave’s inherent geophony – its resonant echo, fluttering reverb and deep acoustic tail – forming a complex and tactile spatial texture.

The concept of the ‘sonic fingerprint’ became central to my compositional approach. Each chamber within Gua Tempurung has a distinct reverberation profile and spatial acoustics. The long decay and natural resonance of the limestone surfaces generate rich timbral nuances that feel almost tactile in their perceptual effect. This tactility, what Brandon LaBelle (Reference LaBelle2010, 94–100) frames within his notion of acoustic intimacy, inspired me to conceive of sound not as something merely heard but as something felt through skin, bone and bodily presence. These sensations motivated the design of Seed of Life 4: Rest and Shelter, where I used low-frequency drones and spatialised ambient textures to evoke the enveloping sonic conditions of the cave.

The sense of touch through sound and tactile aurality was further explored in Seed of Life 4 through strategic use of mid-to-low frequency content, reverberant cues and psychoacoustic effects. For instance, filtering out sub-bass rumbles allowed the textural quality of rain dripping on limestone to emerge as a skin-like sensation in the auditory field. These gestures aim not only to recreate a place but to activate it as a sensorial and mnemonic interface, fostering a form of deep listening that bridges geography, memory and the body (Fazenda et al. Reference Fazenda, Scarre, Till, Pasalodos, Guerra, Tejedor and Foulds2017, 4–5; Blesser and Salter Reference Blesser and Salter2007, 140–142).

Spatial phenomenology – the lived, bodily experience of reverberation, echo and vibration – became both material and method. The way sound travels through the cave, bounces off walls, and hovers in the air creates not just an audible image but a perceptual space. As I walked through the passages, the shifting soundscape altered my proprioception, heightening awareness of scale, distance and bodily presence within the echoic void. These experiences became a blueprint for Bayu Nokturnal II, where I extended the sound world of SoL4 into a live-electroacoustic dialogue with amplified instruments. The acoustic instrumentation chosen for Bayu Nokturnal II, performed by members of the Borneo Ensemble, plays a crucial role in embodying the tactility and spatial awareness of the cave environment. The ensemble’s instrumentation – nose flute, violin, viola, kalimba and piano – was selected for their timbral sensitivity and capacity for blending with field recordings. Their sonic gestures were composed in response to the site’s geophonic cues, acting as musical surrogates for the cave’s natural articulations. This approach extends the philosophy behind Seed of Life 4, which drew conceptual inspiration from Chris Watson’s El Tren Fantasma (Lane and Carlyle Reference Lane and Carlyle2013, 58–60), by integrating live instrumental voices into the spatial dramaturgy. While Watson’s work constructs immersion through acousmatic layering alone, Bayu Nokturnal II reimagines the practice by placing human performance as a corporeal anchor within the sound field, bridging the recorded and the embodied.

Figures 1, 2, 3, 4 and 5 document key recording locations and spectrographic analyses of these sonic fingerprints. These images highlight how natural acoustic phenomena – delays, refractions and resonances – serve as compositional collaborators. Moreover, the absence of archival recordings from Malaysian caves underscores the urgency of documenting such fragile environments. The sonic character of Gua Tempurung, underrepresented in both music and heritage archives, represents an ecological and cultural asset worth preserving. In composing Bayu Nokturnal II, I therefore see myself not only as an artist but as a caretaker of acoustic heritage, capturing sonic traces before they fade into inaudibility.

Figure 1.

Location of Gua Tempurung, Perak National Park, Malaysia (Source: ‘Jelajah Gua Tempurung’. Accessed November 17, 2020. http://myfir2u.blogspot.com/2014/10/jelajah-gua-tempurung.html).

Figure 2.

Route map of Gua Tempurung Cave and primary soundfield recording spot from the main entrance to the Golden Flowstone chamber (Source: Johny Tang, Gua Tempurung - attraction Ipoh City. Accessed May 13, 2020. http://www.ipoh-city.com/attraction/Gua_Tempurung/).

Figure 3.

In-situ field recording activities at Tempurung Cave, Perak, Malaysia (© Ainolnaim Azizol).

Figure 4.

View of the main entrance-exit route of Tempurung cave, Perak, Malaysia (© Ainolnaim Azizol).

Figure 5.

Toom-tone spectral view of Tempurung cave, Perak, Malaysia (© Ainolnaim Azizol).

4. Composing Seed of Life 4: Rest and Shelters

The composition Seed of Life 4: Rest and Shelters was conceived as an immersive electroacoustic narrative shaped by the acoustic ecology of Gua Tempurung. The cave’s sonic qualities, its reverberant chambers, water drips and subterranean air currents provided a foundational palette for the work. My methodology involved capturing high-resolution field recordings using a Zoom H6 recorder with an XYH-6 capsule, set to a 120-degree stereo angle to preserve spatial cues. Inspired by Chris Watson’s El tren fantasma (2011), I sought not only to document a real environment but to sculpt an imaginary one through strategic layering, filtering and spectral transformation. The post-production process began with a detailed spectral and amplitude analysis of the source material. Using spectrogram visualisation, I identified frequency-rich events that defined the cave’s acoustic signature. Frequencies below 30 Hz, mainly structural rumbles, were attenuated to enhance mid-frequency textures such as rain patter, footsteps and distant reverberations. These were curated using waveform editing and processed through quasi-synthesis techniques, including time-stretching, additive-subtractive blending and frequency shifting, allowing for the gradual emergence of both real and imagined acoustic gestures.

A key aesthetic decision was to maintain temporal authenticity while introducing metaphorical elements. This is in line with Truax, Reference Truax2001, 239–243) principle of ‘contextual integrity’ in soundscape composition. Unlike Watson, whose works remain entirely acousmatic, I employed metaphorical listening (Smalley Reference Smalley1997, 112) to translate visual or tactile impressions – moisture, decay and dwelling – into sonic form. For instance, a segment simulating the tactile sensation of damp limestone was achieved by emphasising high-frequency decay tails of dripping water, embedded within low-amplitude reverberation. The aim was to create what LaBelle (Reference LaBelle2010, 33–35, 45–47) calls ‘acoustic intimacy’: a sense of internal dwelling within the space. The dynamic gesture of sonic rupture, where the ambient rain sound abruptly cuts to silence, draws from Watson’s tension and release strategy. This technique functions as an ‘ear-opener’, momentarily disorienting the listener and heightening sensitivity to the following acoustic material (Figure 6). Psychologically, it mimics the dilation of pupils in sudden darkness, preparing the auditory system for finer perception – what Truax, Reference Truax2001, 256–257) describes as ‘sound signal-to-noise rebalancing’.

Figure 6.

‘Ear-opener’ effect – from beginning to approximately 19 seconds (green box), followed by small, ‘timid’ sound gestures (© Ainolnaim Azizol).

As the composition progresses, the soundscape transitions into a more constructed auditory environment, introducing synthesised and processed sounds such as the crackling of broken twigs, stone grinder percussions and the granular rustling of rice grains. These sonic elements were selected not only for their acoustic texture but also for their cultural and historical resonance. Stone implements, once vital tools for grinding grain, reflect early human technological ingenuity and everyday survival practices. Their sonic representation evokes the material culture of prehistoric and rural life. The inclusion of rice grain rustling pays homage to rice as a staple food across many Asian societies, underscoring the intimate ties between sound, sustenance and heritage (King Reference King2017, 58–59). These sonic references locate the composition within a broader anthropological narrative, aligning soundscape composition with ethnographic storytelling. The materials were not randomly scattered but carefully spaced to shape an evolving landscape that moves between fragility and tension. Spatialisation, particularly via binaural cues, emphasises a dislocated, cavernous void that deepens the sense of otherworldliness. The line between naturalistic recording and creative intervention blurs, evoking emotional resonance and historical presence. These spatial gestures not only recreate location but also activate the listener’s memory and imagination, contributing to what Truax and Westerkamp describe as ‘acoustic place identity’.

Geophonic water sounds gradually emerge beneath the soundscape, representing subterranean currents. Their unfolding simulates the physiological experience of attentive listening, akin to the dilation of pupils in darkness or the subtle opening of the tympanic membrane during heightened auditory sensitivity (Moore Reference Moore2012, 91; Sacks Reference Sacks2007, 182). This metaphor aligns with Truax, Reference Truax2001,257) notion of ‘sound signal-to-noise rebalancing’, wherein perceptual recalibration sharpens the listener’s sensitivity to subtle acoustic detail. The symbolic emergence of water not only grounds the composition in geophysical realism but also invokes deeper cultural and psychological associations. Water, as a sonic and ecological element, has historically shaped prehistoric settlement patterns, reflecting the life-sustaining role it played for early human communities (Laureano Reference Laureano2013, 21–22). Simultaneously, its presence operates metaphorically, evoking what LaBelle (Reference LaBelle2010, 33–35) refers to as ‘acoustic dwelling’ – a sonic condition that fosters introspection, spiritual reflection and embodied listening. By aligning natural acoustic features with evolving compositional intent, the piece invites the listener into a state of spatial immersion and temporal contemplation, reconstructing Gua Tempurung not merely as a physical site but as a resonant symbol of human consciousness and spiritual evolution.

To contrast earlier dynamic spatial gestures, a series of monotone drones derived from the cave’s natural resonant frequencies was introduced (Figure 7). This approach echoes Alvin Lucier’s I am Sitting in a Room (1969), where spatial resonance reveals architecture through iterative playback. These drones encourage what Smalley (Reference Smalley1997, 113–114) calls ‘spectromorphological stasis’, allowing temporal suspension and sonic contemplation. Subtle variations in overtone behaviour and reverb decay deepen listener immersion, paralleling Watson’s near-static moments of sonic reflection. Signal processing played a critical role in shaping spectral identity. In Figure 8, a band-pass filtering was used to isolate specific harmonics and introduce spectral overtones, enriching the psychoacoustic experience while preserving the source integrity. Mild distortion added textural tension, similar to colouration techniques by Dhomont and Luc Ferrari, intensifying spatial and emotional affect. These methods bring forth what I term the ‘ghost frequencies’ of the cave – a spectral presence echoing its ancient history.

Figure 7.

Stasis monotone drones at higher frequency register and room-tone at lower frequency register (© Ainolnaim Azizol).

Figure 8.

Example of band-pass filter (left) and saturation (right) approach applied on targeted cave room-tone frequency (© Ainolnaim Azizol).

Caves are symbolically associated with bats, a motif expressed through simulated echolocation pulses from Malaysian bat species (Figure 9). In SoL4, this association is evoked through the suggestion of echolocation calls attributed to the False Serotine Bat (Hesperoptenus doriae), an elusive species native to Malaysia (Francis Reference Francis2008, 76). Given the challenges in capturing authentic calls due to the rarity and elusive behaviour of the species – as noted by bat biologist Juliana Senawi – the composition incorporates echolocation sounds from the broader Vespertilionidae family, utilising verified data from public databases (Warwickshire Bat Group 2024). These high-frequency pulses are spatialised using binaural techniques, allowing the listener to experience the simulated motion of bats as they traverse the virtual cave environment. Similar to Chris Watson’s spatial renderings of birds and insects in works like Cross-Pollination (2014), this technique blurs the line between document and interpretation. The use of ‘flash’ sound cues – short, sharp sonic events – serves to break the ambient continuity, pulling listener attention toward key transitions in the piece. This approach exemplifies what Blesser and Salter (Reference Blesser and Salter2007, 197–199) refer to as ‘aural architecture’, where spatial cues are crafted not only to reflect real places but to guide listener movement and perception.

Figure 9.

Bat echolocation section in Bayu Nokturnal II-SoL4 (© Ainolnaim Azizol).

5. Reimagining for performance: From fixed media to Bayu Nokturnal II

Biomimicry, the creative emulation of natural forms and processes, has long informed innovations in science, architecture and the arts. In music and sound art, biomimicry transcends mere imitation; it becomes a method of reconfiguring natural acoustic phenomena into expressive, symbolic and corporeal gestures. This conceptual strategy draws from the observation that ‘nature’s models can inspire forms, processes, and systems’ in human design across disciplines (Benyus Reference Benyus1997, 2). In sonic arts, this extends to articulations that resonate with ecological and organic realities, offering pathways to reimagine performance and compositional method (Blinkhorn and McConaghy Reference Blinkhorn and McConaghy2024, 255). As LaBelle notes, sound ‘activates space and animates the social’ (Reference LaBelle2010, 204), embedding it deeply within the affective and spatial fabric of experience. In electroacoustic composition, biomimicry has recently been conceptualised as a structural strategy to reframe sonic morphology, texture and environment-responsive performance techniques (Blinkhorn and McConaghy Reference Blinkhorn and McConaghy2024, 257). Drawing from this perspective, biomimicry in Bayu Nokturnal II is not simply an aesthetic choice but a conceptual strategy to embody and transmit the vitality of ecological sound through live performance, fostering a deeper acoustic connection between listener, performer and environment.

Following the fixed-media realisation of Seed of Life 4, the transition towards Bayu Nokturnal II marked a reconfiguration from immersive headphone-based listening to an embodied, live electroacoustic performance. This shift necessitated a reconceptualisation of form, performance practice and spatial dramaturgy, aligning the work with contemporary practices that merge instrumental performance with electroacoustic media. To contextualise Bayu Nokturnal II within a broader lineage, it is instructive to compare it not only with Watson’s El Tren Fantasma, a landmark in narrative soundscape composition, but also with hybrid electroacoustic works such as Matthew Burtner’s Syntax of Snow (2005) and Hildegard Westerkamp’s Fantasie for Horns II (1979).

Burtner’s Syntax of Snow exemplifies the label of ecocomposition, a term first proposed by Robert C. Morgan in 2006 and further elaborated by composers such as Burtner and Di Scipio, as a practice where ecological systems and listening practices directly shape compositional processes. Composed for extended-range glockenspiel and a large container of amplified snow, the piece merges environmental material with instrumental technique, producing a form of embodied performance in which each sonic gesture results from a corresponding physical movement in the snow. The snow and bells operate as a single composite instrument, and the gestures become a form of aural score, where environmental texture replaces traditional notation. As Burtner explains, snow communicates complex ecological information, from temporal cues to spatial orientation, when attentively heard. This notion reflects his broader ecoacoustic ethos, developed through his EcoSono project, where digital sound design interfaces with environmental interactivity to create site-responsive music (Burtner Reference Burtner2011, 142; Keller and Capasso Reference Keller and Capasso2006, 3). In Bayu Nokturnal II, a similar ecocompositional approach underpins the structure: biomimetic instrumental gestures respond to biophonic and geophonic recordings of the cave environment, guided not by metric notation but by environmental behaviour and memory. Performers rely on deep listening and intuitive synchronisation, embodying the aural score through reactive gestures and acoustic sensitivity.

Westerkamp’s Fantasie for Horns II offers another compelling parallel. The work overlays processed horn calls with environmental recordings from Vancouver’s soundscape, positioning the horn not merely as a musical voice but as a bridge between human and ecological expression. Through techniques such as filtering, tape manipulation and spatial placement, Westerkamp constructs an immersive field in which instrumental phrases rise from, dissolve into or animate the surrounding environmental textures. This aesthetic finds resonance in Bayu Nokturnal II, where instrumental and environmental sounds are interwoven in a dramaturgical arc that mirrors the cave’s acoustic ecology. Both works emphasise the permeability of sonic boundaries – between performer and environment, sound object and gesture – and highlight how instrumental sound can both shape and be shaped by place.

These works actively incorporate live instrumental performance within complex environmental and electroacoustic sound fields, offering pertinent parallels that help illuminate Bayu Nokturnal II’s integration of instrumental and fixed-media elements. The biomimetic gestures, spatial interplay, use of aural-feedback scoring and evolving tension–release form of Bayu Nokturnal II are enriched by such comparisons. They situate it within a broader ecocompositional practice of ecological electroacoustic performance where gesture, field and memory are dynamically entangled. Reflecting the influence of ecocomposition, the work was notated in a grid cell table format using Scientific Pitch Notation, standard dynamic markings and articulation symbols, with additional performance notes describing interpretative approaches to gesture and sonic intent. Instead of using conventional time signatures, the work adopts a time-based matrix system, aligning with its environmentally derived structure. This notational approach prioritises temporal flow and ecological mimicry over metrical precision, encouraging performers to respond to the sonic behaviour of the fixed media with a blend of discipline and improvisational listening. In doing so, the score becomes more than a set of instructions; it serves as an aural interface, inviting performers to engage with the cave’s sonic memory through embodied awareness, fostering a shared ecological narrative between sound, space and listener.

Structurally, Bayu Nokturnal II follows an arch-shaped form, a compositional model characterised by a gradual intensification of sonic material towards a climactic centrepoint, followed by symmetrical release. This model, closely related to the ‘pyramid’ form, is effective in shaping psychological and affective trajectories. The composition begins with sparse textures and spatialised cave recordings, steadily builds in complexity through the introduction of instrumental layers, and culminates in a dense sonic convergence before receding into spectral stillness. This approach draws from Wolfgang Rihm’s notion of ‘tension and release as dramatic inevitability’, where form emerges from energetic contour rather than pre-fixed schematics. As Rihm describes, ‘form arises out of sound’s own tension, from the need for breath and silence that follows intensity’ (Rihm, Reference Rihm, Schwartz and Childs1995, 248). This ethos underpins the work’s arc: field recordings generate the ground layer of tension, while live instruments catalyse and respond to that intensity through evolving motifs, before collectively dissolving into a sonic denouement. Compositional structures were built around modular ‘cells’, which functioned like porous frames: some were closely aligned with the fixed media’s dynamic curves, while others introduced temporal shifts that created contrapuntal tension. For instance, a segment involving harmonics in the viola and violin is stretched against a sustained drone in the soundscape, creating friction and resonance between stable and unstable spectral regions. Over time, the instrumental voices shift from mimetic gestures to more autonomous sonic explorations, suggesting a narrative arc – from acoustic camouflage to emergence and assertion.

The selected instrumental ensemble – Turali nose flute, violin, viola, kalimba and prepared piano – was chosen for their capacity to blend seamlessly with the spectral textures of the original soundscape and to express gestural affinities with the cave’s biophonic and geophonic environment. These instruments were not imposed upon the soundscape but composed in responsive dialogue with it. The fixed media component, derived from field recordings and electroacoustic transformations, functions not as a passive ‘background’ but as an active spatial presence, an immersive sonic terrain that continuously interacts with the instrumental voices. At times, the soundscape leads; at others, it reacts. The interaction is fluid and co-creative rather than hierarchical. For example, kalimba phrases mimic the rhythm and decay of mineral water drips, while the flute’s trills and glissandi suggest the erratic flight of bats, responding to the echolocation pulses embedded within the fixed media. This interdependence creates a layered dialogue in which the soundscape sets up a condition of listening, and the instrumental parts amplify or disturb it, sometimes echoing spectral features, other times adding tension through contrast.

The relationship between instrumental phrases and soundscapes is not hierarchical but dialogic. Contrary to the implication of the word ‘background’, the soundscape in Bayu Nokturnal II functions as an active agent, shaping the pacing, dynamics and expressive arcs of the live parts. The fixed media elements, comprising geophonic cave acoustics, filtered bat echolocations and spatialised biophonic textures such as water droplets and insect calls, are not static backdrops but living sonic entities. They engage in continuous exchange with the performers, cueing shifts in intensity, guiding timbral transformations and creating moments of tension and release that are integral to the dramaturgical structure of the work. This dialogic interplay fosters a performative ecology in which human and non-human sounds co-compose the evolving sonic narrative. For instance, the kalimba echoes the rhythmic flutter of water drops, while the trilled nose flute mimics bat trajectories. These gestures are not incidental but structurally embedded within each musical cell, forming what may be understood as a call-and-response ecology, or what Truax (Reference Truax2012, 105) terms ‘acoustic belonging’, where sonic identity is shaped through environmental interplay.

Their relationship oscillates between convergence and divergence, sometimes blending seamlessly, at other times creating dissonant interplay that reflects ecological instability or psychic tension. The idea of ‘intricate musical dialogue’ is made manifest through this dynamic choreography: not only do instrumental phrases echo environmental motifs but they also reshape them, turning passive echoes into active sonic agents. As the composition unfolds, this dialogue becomes increasingly textured, mirroring the complexity of the cave’s acoustic ecology. These motifs evolve across the arch form. In the first section, the soundscape dominates, with sparse instrumental punctuations emerging subtly. As the work ascends, layering intensifies, with violin harmonics, trilled flute and pizzicato prepared piano coalescing into overlapping biomimetic textures. At the climactic apex, instrumental phrases briefly overtake the soundscape, an inversion that represents human presence imprinting on a primordial environment. Following this peak, instrumental retreat mirrors the sonic entropy of the cave, where echoes decay and stillness returns. This shaping is reinforced by timbre and spatialisation. Instrumentalists were placed around the audience in stereo-diffusion, spatially blending with the fixed sound field.

The tape-based soundscape drones and string instrument frequencies were experimentally tuned to approximate bodily resonance zones (Figure 10), specifically those of the skull, throat and nasal cavities (Håkansson et al. Reference Håkansson, Brandt, Carlsson and Tjellström1994, 140–142) to invite a form of corporeal listening and amplify affective presence. While these frequencies are not individually tailored and rely on averaged anatomical data, their purpose in this context is not to achieve scientifically precise stimulation, but rather to explore the potential of resonance as a symbolic and perceptual device. The approach is thus more poetic than prescriptive, aiming to gesture towards embodied experience rather than guarantee it. In this way, it aligns with Alvin Lucier’s proposition that performers act as ‘resonators of architectural space’ (Lucier, 1995, 13), reinforcing the notion that both space and body can filter and amplify sonic energy in perceptually meaningful ways. Within this framework, Bayu Nokturnal II transcends mere adaptation; it becomes a living, performative archive in which ecological metaphor, sonic tactility and embodied ritual converge. Rather than striving for biometric precision, the composition experiments with psychoacoustic suggestion, an invitation to listeners to engage bodily, imaginatively and culturally with sound. This reflects a broader ethos of soundscape composition not as documentation, but as active dramaturgy: a re-enactment of memory, site and spiritual resonance through sonic form.

Figure 10.

Natural resonance frequency mapping of a human neck-head organ (© Ainolnaim Azizol).

Challenges arose in aligning the live instrumental gestures with the micro-rhythmic and spectral behaviours of the fixed media. Unlike traditional scores, which often function linearly, the performative structure required an expanded listening practice from the ensemble – attuning to breath-length phrases, dynamic swells and spectral overlaps rather than strict metric cues (Figure 11). This demanded a heightened sensitivity to timing, especially in moments where silence or near-silence played a structural role. One critical solution involved using graphic and time-based notation to indicate sonic intent and gestural contour rather than fixed rhythm, allowing for real-time responsiveness and deeper immersion. Throughout, the instrumental and soundscape elements evolve in tandem.

Figure 11.

Full score of Bayu Nokturnal II (© Ainolnaim Azizol).