Before releasing the indie classic On Avery Island, there were a handful of self-released cassettes accredited to Neutral Milk Hotel. Most of the material was thrown together by singer/guitarist Jeff Mangum and exclusively distributed to other members of the experimental Elephant Six collective. One of the earliest is a piece from 1991 called Invent Yourself a Shortcake.
At this point, the Neutral Milk sound is radically different from what the band would come to be known for. There's a lot of sound collage / musique concrete to be found here with song titles like "Random Noise," "More Noise" and "Spooky Sounds." There are a few songs with no musical elements at all such as "Prank Call" and "Digestion Machine," and there are even a few pieces like "Charlotte" that are pure noise rock. However, there's still a bit of folky indie rock to be found, with pop songs like "My Dreamgirl Don't Exist," and "Synthetic Flying Machine" which eventually made it's way onto In The Aeroplane over the Sea.
While obviously not on par with their later, more official releases, this is a recommended listen for anyone into early 90's indie.