A trove of early Nirvana demo tapes has surfaced online, the late-'80s recordings of Kurt Cobain and co. being shared on YouTube by a musician who says they were personally given to him by the late frontman. Hear them below.

Read more: Hear Nirvana's “Teen Spirit” as a pop-punk jam

The four tapes' audio was uploaded by Washington musician John Purkey, as reported by NME, and includes demos for Nirvana's debut album, Bleach, recorded during the band's first sessions at Seattle's Reciprocal Studios in 1988. The Bleach demos feature Melvins drummer Dale Crover, while another tape comprises Nevermind demos with his replacement, Chad Channing, on the drums. Channing, of course, was eventually succeeded by Dave Grohl.

Purkey also offers a brief explanatory video (see the very last clip) recounting his experience with Cobain and Nirvana while watching them woodshed their early material in his home state. As noted by Spin, Purkey performed in a handful of bands in Tacoma, Washington, during Nirvana's early days, and his collection of demo tapes—while some include previously released material—offer an insider's look at the embryonic state of the alt-rock trailblazers.

Purkey says he kept the tapes hidden inside two metal boxes for years. One accompanying cassette was stolen from a friend's car, and two others were sold off by the musician—the collection was also apparently once threatened by a monsoon. Explore the abundance of Nirvana audio here:

Watch more: Who are the best alternative artists ever?