The nice thing about out-of-print recordings is that, if someone takes the initiative to post some MP3s online, they are normally not hassled to take them down. And when the music in question is avant-garde stuff that was never committed to CD in the first place, you can really go crazy, just like the Avant Garde Project did. Their enormous archive includes touchstones are disparate as Henry Kaiser, Iannis Xenakis, Stravinsky, Schoenberg, Berg, Cage, and a great deal of electronic works. Beware, although these are free, they are FLAC files and will undoubtedly take a long time to download. If my dad were still alive, he would worry for my tastes.