Introduction

We introduced the phenomena of distribution in Unit 1, the patterns that emerged from co-occurrence restrictions. The phenomena we analyzed involve the distribution of segments such as Kikuyu vowel co-occurrence. We examine a different type of phenomenon, the phenomenon of tone, starting from this chapter. Tone is related to pitch, a term that may be familiar to you. Pitch is correlated with the rate of vocal cord vibration in the production of voiced sounds. This rate is called the fundamental frequency or F0. The higher the F0 of a voiced sound, the higher its pitch is perceived to be. Pitch is a perceptual term, referring to the perceptual sensations in hearing voiced sounds. Tone, on the other hand, is a linguistic term, referring to pitch when it is used to signal meaning differences in languages. Just as English uses voicing to signal meaning differences such as bɪt ‘bit’ versus pɪt ‘pit,’ languages may use pitch variations to differentiate meanings. For instance, though pù ‘European’ and pû ‘cave’ may consist of identical sounds in Mende, they differ in meaning because their tones (marked by ` and ˆ) are different. When pitch variations signal contrasts in meaning, we refer to them as tones.

Just as segments may be subject to restrictions when they co-occur, tones are subject to restrictions as well, resulting in predictable tonal patterns. Tonal restrictions may result from the co-occurrence of different tones, the co-occurrence of tones with segments, or the constraints on tones imposed by phonological or morphological units. In this chapter, we introduce a case of tonal distribution involving the co-occurrence of different tones. The data come from Mende, a Mande language spoken in Sierra Leone. The co-occurrence of tones is highly restricted in Mende nouns, with only a small number of attested tone patterns. To gain an understanding of the Mende tonal restrictions, we conduct two analyses. In one analysis, we treat tone as a property of segments that bear the tones. In a second analysis, tone is analyzed as a property of morphemes. The goal of this presentation is to develop your understanding of the view that tone, while realized on segments on the surface, may behave as if it were independent of them. This view has led to the development of the theory known as Autosegmental Phonology.