When Bob Dylan put out his tenth album in nine years in 1970, he was still at the center of a storm. Viewed as the voice of a generation in a dangerous, turbulent era, people were not prepared for the double-disc data-dump that was Self Portrait.

It contained over 73 minutes of material recorded over the course of a year—silly song sketches, live tracks, hokey covers, everything but the kitchen sink. Longtime Dylan scholar Greil Marcus’ Rolling Stone review of the record began, “What is this shit?”

There are a couple different theories on that. It was either Dylan’s attempt to throw people off by putting out an intentionally alienating album or a proto-version of Dylan’s long-running, vault-raiding Bootleg Series, meant to cash in on the then-current craze of bootlegging him.

It picks up some interesting live performances with the Band, including the best-ever version of “Quinn the Eskimo (Mighty Quinn),” which was later a hit for Manfred Mann. And the covers are mostly brilliant, with Dylan continuing to use the throaty singing voice he introduced on Nashville Skyline the year before but dropping it whenever it served the song to do so, practically admitting it was a put-on in the first place.

All of this may have been baffling at the time but today it’s invaluable; an overstuffed grab bag of Dylan getting strange as the decade he helped define—and came to loathe—drew to a close.