It's the beginning of five preludes from Bach's WTC all played at once, each one in three different keys. It's a file I use to demonstrate the effect of Werckmeister III temperament on Bach's music by playing them in both correct and incorrect keys. I usually play them one track at a time in Digital Performer, but my old version won't work on my current laptop, and so I opened them in Quicktime, which could only play them all at once, most of them in alarmingly rapid tempos.

Somebody give me fifteen Disklaviers to work with and I'll change the history of music.