Music by Philip Glass.
Published by Dunvagen Music Publishers.

two soprano saxophones

Play used two soprano saxophones, each given two notes to play against each other, in a constantly shifting pattern. What was heard was never exactly the same, but it never really changed very much. I wrote six or eight little sections like that and put them on a tape with 45 seconds of music followed by 45 seconds of silence followed by the next section of music and so on.
— Philip Glass