Inner voices
Inner parts of a polyphonic texture between the top and bottom parts, such as alto and tenor.
What it means
Inner voices are the parts of a polyphonic texture that lie between the uppermost part (usually the melody) and the lowest (the bass). In four-part choral writing these are the alto and tenor. They secure the harmony, fill out the chords and, through their voice-leading, determine how fluent and lively a texture sounds.
Musical use
In the theory of part-writing, the rules of good voice-leading apply to the inner voices: the smallest possible steps, common tones retained, no awkward leaps and no parallel fifths or octaves. In Renaissance and baroque counterpoint, by contrast, the inner voices are often independent lines with their own melody.
They should be distinguished from the outer voices (top and bottom), which are heard most clearly in the texture. They differ from filling parts in that filling parts merely complete the chords, whereas inner voices can carry their own weight.
Performance practice
When you sing or play an inner voice, listen to the top and bottom parts and blend with them. Practise your part alone as well, because it is often less melodic than the top line and must still sit securely.