The piece opens with steady rhythmic movement, introduced at the beginning by two wooden blocks, covered with sandpaper. This movement is taken over by the strings and other instruments and is occasionally opposed by different rhythmic patterns, colliding with the original rhythm. 

As the piece progresses, these collisions become less and less harsh and at the end of the piece all the instruments play in rhythmic unison. The lyrical parts serve as a contrast to the continuous rhythmical flow of the piece.
Collisions” was commissioned by the Koussevitzky Foundation