Polyphonic
With several simultaneous voices.
What it means
Polyphonic is music in which several voices sound simultaneously. Two basic kinds are distinguished: polyphonic texture in the strict sense, in which the voices are led independently and each has its own melodic shape, and homophonic texture, in which a main voice is accompanied by chordally led voices. Both kinds rarely occur in pure form; most movements mix them.
Musical use
The development of polyphony is a core piece of European music history. It begins in the Middle Ages with the addition of a second voice to liturgical chant and leads through the art of the Renaissance, in which four, five, and more voices of equal standing are worked through in imitation, up to the fugue of the Baroque. In parallel, with the figured bass, the predominance of melody and accompaniment arises. For the listener, polyphony means that several lines are to be followed at once; for the composer, that every voice must be meaningful in itself and coherent in combination — the twofold requirement that grounds counterpoint.
Performance practice
With polyphonic movements, work out each voice individually first, then listen deliberately to one voice while you play or sing the whole texture. Make sure that no voice permanently becomes an accompaniment when it is meant independently. Make entries audible without their jumping out. Keep the articulation of the same motif the same in all voices. On the piano it helps to practise voices in pairs; in ensemble, rehearsing in small groups is worthwhile.
Bear in mind that polyphonic and homophonic sections alternate within the same works: a texture worked through in imitation can pass into a chordal one, and this change organizes the form. Mark such places and shape them. Take care that middle voices remain audible, because they are easily neglected in practice. Practise voices in pairs, on the piano as well as in ensemble. Practise difficult passages in voice pairs before all voices come together.
Check with old editions whether voices were transposed into modern clefs, because that affects the register and thereby the scoring.