Forgive me, but let’s open with some math. Depending on what sounds you consider canonical—never an easy decision in Frank Zappa world—the enigmatic composer released somewhere around 60 albums in his lifetime. His first, the game-changing avant-rock experiment Freak Out!, came out in 1966, when he was 25. Twenty-seven years later, he died from prostate cancer at age 52.

That means he averaged roughly two projects a year during his recording era—an absurd figure on its own. But that’s not including the mind-boggling amount of posthumous releases—expanded box sets; grainy-sounding, glorified bootlegs; odds-and-sods rarity patchworks—carefully excavated from his vast vault in the decades since. (Feel free to track down those numbers yourself. My brain hurts, and I suddenly feel guilty about that hard drive of prog-rock demos I haven’t fleshed out.)

All of this archival material is fascinating for Zappa-heads, and some of it approaches the realm of revelatory. And that high bar of quality proves, despite Zappa’s antsy shapeshifting and intimidating prolificacy, that his “official” catalog only teased a fraction of the wild ideas jumping around his brain. The latest proof is Funky Nothingness, a 3-CD (or 2-LP) set presenting an alternate-universe Zappa path—a missing link between the fiery, fusion-meets-blues-rock swirl of Hot Rats and the freewheeling musical buffet of Chunga’s Revenge.

The tracks, most previously unreleased, were recorded in early 1970 at L.A.’s Record Plant, utilizing a tight crew of players: multi-instrumentalist Ian Underwood, singer-violinist Don “Sugarcane” Harris, bassist Max Bennett, and recently recruited drum virtuoso Aynsley Dunbar. (The one deviation is notable: The title cut, a pleasant but inessential blues throwaway, was tracked during a 1967 session for what became Uncle Meat.)

The chemistry between that group was intense—even their longest, most meandering jams are worth savoring for one reason or another. A raunchy, 12-minute edition of Lightnin’ Slim’s blues piece “I’m a Rollin’ Stone,” later reshaped into the backing track for 1974’s “Stink-Foot,” is full of exquisite detail, including a Zappa guitar solo that crests into a hammer-on tornado. Equally revealing is the nine-minute “Basement Version” of “Chunga’s Revenge,” a starker and more psychedelic approach than the jazzy, skronky shape it later took. With Underwood’s glimmering electric piano and Dunbar’s supple, subtle drum groove, it suggests Pink Floyd with R&B/funk chops. (Speaking of which, here’s a reminder of that time at a 1969 festival when Zappa soloed all over Floyd’s “Interstellar Overdrive”—a sadly one-off collision of worlds.)

Admittedly, it’s harder to recommend the looser-than-loose “Basement Jam,” which rarely exceeds the low expectations of its afterthought title. (Zappa tosses off solid, if sorta entry-level, versions of his signature guitar moves, and the rhythm section just kinda bangs around.) But even within all this stretching out and searching, there’s a graspable sense of purpose: The widely bootlegged “Twinkle Tits,” for example, morphs from a buttoned-up, classical-styled waltz into a blues-rock workout with an onslaught of smoking solos.

With so many legacy-artist posthumous sets, it’s hard to avoid a certain level of brain mush. The final stretches often feel like pointlessly processed outtakes of alternate takes of fake takes of imaginary takes. It’s like extracurricular archaeology, and it’s often not very fun. But even when you’re working up a sweat with your shovel, Funky Nothingness rewards the strain.