Piano Phase, composed by Steve Reich, is a fascinating piece of minimal music for 2 pianos (or marimbas).
It uses 3 short musical phrases, with 12, 8 and 4 semiquavers respectively, that are repeatedly played by the 2 pianos, starting out in parallel (with piano 2 fading in over some repetitions). Over the next repetitions piano 2 speeds up very slightly until it is one semiquaver ahead to piano 1, then more repetitions with this fixed offset follow and explore the different emerging rhythm and sound interplay. This process continues until piano 2 has advanced to the point where it is again in sync to piano 1. Similar full cycles, together with a fade out/fade in of one piano is done also for the next 2 phrases. Details and a better description can be found, e.g., at Wikipedia.
This rather technically sounding description leads to a very subtle effect how the phrases interact in their shifted positions – every different phase shift sounding subtly different – experience this yourself by listening, e.g., to this performance by Art Murphy and Steve Reich.
This image is my static interpretation of this music – horizontal lines are like the lines of the score for the music, two adjacent rows corresponding to the 2 pianos. Color represents the note pitch; fading from or to black represents the fading of the respective piano.
The 3 different parts corresponding to the 3 different phrases can be seen clearly, separated the the black parts of the fade out/in of one of the pianos, also visible is how the phrases are getting shorter.
The acceleration phases as well as the resulting new phase shifts nicely stand out in the color patterns.
All in all, the representation is faithful to the musical score except for the choice of the number of repetitions that are given as possible ranges in the original score. These are fixed here so that lines for the different phases result in equal lengths in the image.