If your browser/MP3 player doesn't read the title correctly, it's "PI-ssacaglia". And no, that's not a typo.

This is a Passacaglia whose primary theme is the first digits of the mathematical constant, Pi. (3.14159265) for string quintet.

There are also two other variations in the piece derived from the digits after the first ten in Pi, but I won't tell you which ones. :P