Daniel Barenboim: Polyphony in music

The only really polyphonic instruments are the piano, all forms of harpsichord or clavichord, the guitar, organ and the harp. You can create an illusion of polyphony if you play Bach unaccompanied on a cello or violin, but by nature these instruments are monophonic. Music, however is polyphonic by nature, and harmony is possible only in polyphonic terms. I have often found it necessary to point out to both singers and instrumentalists the polyphonic nature of music - the relationship between the vertical and the horizontal, the horizontal being the separate lines of melody and the vertical the harmonies, the polyphony. If the relation between the horizontal and the vertical is incorrect, then the whole interpretation is incorrect.