Theme and Variations
In the right hands, theme and variations can musically approximate thought: one idea held in the mind, turned over, examined from every angle. I think of the middle movement of Mozart's B-flat Major Piano Concerto, K. 456. Its eight bar theme in G Minor expresses such sadness, such quietness in the face of loss, and then in the last four eighth-notes, it gently ends in B-flat Major. A simple cadential figure briefly touches a sunnier world. It's as if the experience of pain brought to mind memories, souvenirs, of when hope was possible. The theme is repeated, variations ensue, and the thought process of working through that initial idea begins. This movement is a true masterpiece, and all the romp and jollity of the last movement cannot mask the memories of what came before.
Albert Fuller used to say, "What's past is prologue." Yet you cannot go backwards. You cannot touch the past. Music is experienced as memory and emotion, which is also how we process the experiences that change our lives.