downstep (n.)

A term used in the PHONOLOGY of TONE languages, referring to a lowering process which applies to the second of two high-tone SYLLABLES. A downstepped high tone would be slightly lower than the preceding high tone, but not so low as to be equivalent to a low tone. The process has been widely observed in African languages. Less commonly, the opposite effect, upstep, has been noted, where successive high tones become progressively higher. Downstep is phonologically CONTRASTIVE, and is usually distinguished from downdrift, a sequential process whereby high tones after low tones become progressively less high throughout an intonational unit. These effects have been described more generally as ‘register lowering’ or ‘key lowering’. Declination is often used as an equivalent for downdrift, but this term also has a more general phonetic use (‘F₀ declination’), referring to a gradual descent of pitch level and narrowing of pitch range throughout an utterance, partly as a result of reduction in subglottal air pressure, as speakers use up the breath in their lungs. Such effects, of course, are not restricted to tone languages.