Archive.org offers you a tremendous amount of tunes, all accessible online. And it's not just any tracks: dozens of forgotten tapes, full of subversive treasures, referenced by the amazing online archive website.
The collection of about 30 Go, was quietly left on the website noise-arch.net since 2011. It comes from the Myke Dye's audio library, a radio animator for the Canadian underground and communal radio CKLN-FM, on air from 1983 to 2011.
In this rather strange list you can find “tape experimentation, industrial, avant-garde, indy, rock, diy, subvertainment and auto-hypnotic material”
Depending on your Internet connection, the full downloading should take you anywhere between a few minutes and a few hours, maybe a few days the really unlucky ones. But be patient, it's clearly worth it.