Here's a funny one that we found at a record store in Amsterdam.
"Ten years after the recording of Last Date, while cleaning his apartment, Mengelberg found a rehearsal tape containing a recording of an 18-minute run through of "Epistrophy" at Cafe de Kroon, Eindhoven, Netherlands from the day before the concert. Mengelberg sent the tape to Bennink, along with a letter requesting that he release it on the Instant Composers Pool label. The track was issued on LP by ICP in 1975, backed by a recording of Mengelberg playing a duet with his parrot, Eeko"
We won't lie to you: this isn't great stuff. It's a low quality audience recording of one track, backed with a short and vaguely interesting home recording that is probably better appreciated from an ambient sense than musical. But, it's random oddball releases like this that make the world go around.
VG+ condition. There's a tiny square sticker on the back that someone used to catalog it with ("480").