High tone lowering and raising in Tsua
The Tsua language is an Eastern Kalahari Khoe language of Botswana (Chebanne 2014). Tsua tone production displays complex Fundamental Frequency (F0) trajectories. Lexical data show that this language has three tone levels: High (H), Mid (M), and Low (L), with the following surface tone melodies: [HH, HM, HL, MM, MH, ML]. High tones may be lowered when they occur following voiced obstruents, aspirated obstruents or the glottal fricative /h/ in root-initial position, a typologically rare pattern. This results in two depressed melodies: depressed HM
[DH-M] and depressed HL [DH-L]. Both clicks and non-clicks participate in this interaction. We refer to this tonal depression pattern as High Tone Lowering (HTL). HTL may be formally accounted for via the Low tone insertion rule: ∅ → L / [-sonorant, +slack] ___ H [-H] #. Recent analysis suggests that Super High (SH) tones are derived from /H/ when docked to the high vowels [i], [u] and are not phonemic. For example, underlying /HL/ tűù “to collect and remove ash” is produced with SH-L tones on the surface. We refer to this as High Tone Raising (HTR). Elderkin (1988) reports a similar finding in Ju|ʼhoan in which a sequence of successive extrahigh tones is only found in click-initial morphs when the final vowel is [i] or [u]. It may be that an Intrinsic F0 (IF0) effect from the Tsua high vowels was a historical factor that led to the genesis of HTR. Given that voiced, aspirated and /h/ consonant types depress a root-initial H tone and the high vowels [i], [u] raise H tones, the paper considers phonetically-driven origins of these patterns.
Keywords: tone; depressor consonants; high vowels; Khoisan; Intrinsic F0