A note on nomenclature: this unreleased 1968 album was entitled A Woofer in Tweeter's Clothing. However, it went unreleased, and the band's second--completely different--album borrowed that name. For that reason, we generally just stick with the descriptive "Halfnelson Demos" when talking about this here piece of work.
Unreleased, yes (two of the tracks, "Roger" and "Saccharin and the War," were rerecorded for the band's subsequent album). And for the life of me, I couldn't tell you WHY there's never been an official release. At any rate, you can find it easily enough on teh intertrons. And you should if you're any kind of Sparks fan, because this is revelatory stuff: the band seemed kind of out-of-time from the beginning; you certainly couldn't place them in any particular musical period. But these demos reveal the shocking truth: Sparks in its initial incarnation was as an honest-to-god sixties psychedelic garage band, not unlike the sorts of acts you'd hear on Rhino's Nuggets anthologies. Just listen to "Join the Firm" or "The Factory!" It's easy to imagine one of these appearing on one of those. Whaddaya know.
It would definitely be one of the highlights, though--it may not blow your mind, but it's pretty cool, atmospheric stuff. "Arts & Crafts Spectacular" is a song about…well, the title about sums it up. It is cool and strange. Likewise "Johnny's Adventure" (no relation to Indiscreet's "It Ain't 1918"). "The Animals at Jason's Bar and Grill" is about what happens when the animals want to eat there. Naturellement! Basically, there's a lot to grok here, and grokking is highly recommended, especially given that you'll have to download it for free--you couldn't pay for it if you wanted to.