A single melody is enough to qualify as music — sometimes, indeed, as great music. When people sing in the shower and when parents sing to their babies they are producing melody, and that is all, to everyone’s full satisfaction. The same was true of the early Christian church, whose music, Gregorian chant, consisted of more than two thousand different melodies — and melodies alone.

Today, however, after a long and complicated historical development, it seems very natural to us to hear melodies together with other sounds. We are accustomed to hearing a folk singer singing and playing a guitar at the same time — accompanying herself on the guitar, as we say. In church, the congregation sings the hymns while the organist supplies the accompaniment.

Two concepts of basic importance in thinking about the way pitches sound together with each other are harmony and texture.