Downstep

Downstep is a phenomenon in language where when two syllables have the same tone (for example both have high tone, or both have mid tone), the second syllable is lower in pitch than the first.

Two main kinds of downstep can be distinguished. The first, more usually called automatic downstep, downdrift or catathesis, occurs when high and low tones come in the sequence H L (L) H; then the second high tone tends to be lower than the first because of the intervening low toned syllable. This phenomenon is common in African languages. It has also been argued that it is this same phenomenon which causes English sentences such as I really believe Ebenezer was a dealer in magnesium or I bought blueberries, bayberries, raspberries, mulberries, and brambleberries (if these sentences are pronounced with a falling intonation) to fall gradually in pitch, with each accented syllable (here underlined) slightly lower than the last.

Downstep proper or non-automatic downstep on the other hand is a phenomenon found especially in West African languages such as Igbo when of two high tones in succeeding syllables (that is, in the sequence H H) the second is lower than the first. In such languages, when two high tones come one after the other either they are at the same height or (if there is a downstep) the second one is lower; the second high tone is also lower than the preceding one if there is an intervening low, in the sequence H L H as described above. Thus the high tones in a simple sentence tend to descend downwards from the beginning to the end of the sentence in a series of steps, a phenomenon known as tone terracing.

The symbol for this second kind of downstep in the International Phonetic Alphabet is a superscript down arrow, (^↓). It is common to see a superscript exclamation mark, (^!), used instead due to typographic constraints.

It has been shown that in most if not all cases of downstep proper, the lowering of the second high tone is caused because an intervening low-toned syllable has dropped out, i.e. what was formerly H L H has become H H. This missing low-toned syllable creates what is known as a 'floating tone'. An example occurs in Bambara, a language spoken in Mali. In this language, the definite article is a floating low tone. With a noun in isolation, it docks to the preceding vowel, turning a high tone into a falling tone:

However, when it occurs between two high tones, it downsteps the following tone:

Japanese pitch accent may be compared to this. About 80% of Japanese words have an evenly rising pitch, something like French, which carries over onto a following unstressed grammatical particle. However, about 20% of words have a drop in pitch between syllables, or before a grammatical particle. An example is

In isolation like this, the first word has a high-low pitch, whereas the second and third are homonyms with a low-high pitch. (The first syllable is only low when the word is said in isolation.) However, all three are distinct when followed by the nominative particle ga: