Music in Twelve Parts

Music in Twelve Parts is a set of twelve pieces written between 1971 and 1974 by the composer Philip Glass.

The eleven instruments in this work cycle are played by five musicians: three electric organs, two flutes, four saxophones (two soprano, one alto, one tenor) and one female voice. Only the organ can be heard throughout; the other instruments are not playing simultaneously the whole time. Only one piece was originally written, which was called "Music in Twelve Parts" because it was originally intended to have twelve lines of counterpoint harmony, but when Glass played it to a friend, she asked him what the other eleven parts would be like. He found the misunderstanding interesting, and wrote another eleven parts over a period of three years. The entire set can be over three hours long when performed. In these works, Glass uses repetitive structures often associated with musical minimalism. Despite this, many of the works display a great deal of variety and invention. The music develops slowly, and there are long periods during which a casual listener would not notice any change. If one listens closely, however, this is seen to be an illusion, since patterns actually change form almost continuously, though nearly imperceptibly. The pieces are therefore challenging to the listener, but they have still enjoyed a significant level of popularity and are often cited as a major work of the second half of the 20th century. The works show a great emphasis on development and slow alteration, with different pieces utilizing different techniques for development.

Andrew Porter for The New Yorker magazine (1978) wrote of the transitions from one track to the next:

A new sound and a new chord suddenly break in, with an effect as if one wall of a room has suddenly disappeared, to reveal a completely new view.