The A natural minor scale has some historical connections. Before major and minor scales became prevalent in Western art music, music, especially the early liturgical music that has been so influential on Pärt, used a system of modes. The idea of musical modes was known to the ancient Greeks, and each was said to have a specific character which could strongly affect the mind. The church modes are formed by using the notes of the C major scale (i.e., the white keys on a piano) but starting at different notes in each mode. A scale of A with no black keys is in the Aeolian mode. Since all natural minor scales derive from the white keys on the piano played from A to A, in choosing the A minor scale Pärt is acknowledging his debt to early church music, or at least affirming his affinity with it.