Just after a spring tour’s conclusion in 1974, Frank Zappa and his Mothers of Invention reconvened on a June afternoon in the band’s Sunset Strip rehearsal space, invited over a modest crowd of L.A. beautiful people, and performed a concert-length set taped for a future television special. The special never aired. Finally, five decades later, here it is, previously unseen, with an accompanying soundtrack on three-LP vinyl and 2-CD configurations, comprising what, for many Zappa fans, is the holiest of grails.

Zappa, never one to shy away from the role of self-deprecating malcontent, immediately christens the production space as “cheaper than cheap,” then proceeds to conduct and perform his way through a tantalizing and vastly terrific show with his ultra-talented ensemble. This was a band, and a time in Zappa’s career, that have been assessed by devotees as possibly the best in terms of musicianship and repertoire. Certainly, coming fresh off of the road saw the group in the sharpest of modes, exemplified by the lockdown percussion work of the incomparable Ruth Underwood and the splendiferous drumming of Chester Thompson. Add in the majesty of George Duke on keys, Tom Fowler on bass, the multi-instrumentalist delights of Napoleon Murphy Brock on vocals, and Jeff Simmons on guitar, and it’s no wonder this unit achieved exalted status.

As for the show, it is expectedly tight and virtuosic, yet silly and loose in all the right places. The gorgeous sprawl of extended soloing is present and well-accounted for, particularly on a sparkling “Inca Roads,” or the funky, late-set highlight, “More Trouble Every Day,” with Zappa’s explorative guitar work as compelling as ever. The Zappa archive previously has released some concerts from the spring 1974 tour, and they, too, are corkers. No doubt, a golden era.

Perhaps what is the difference between those concert appearances and this proposed TV show is the relatively little bawdy, profane chicanery that a typical Zappa performance provoked and allowed for- and TV censors likely would not. Frank, seemingly aware, wryly offers, “expletive deleted,” during the take of “Oh No.”  Other than that rather inconsequential detail, it’s a marvelous example of these Mothers at the top of their game in ‘74.

Rejoice that Frank’s son, Ahmet, delivered such a superlative job on the Blu-ray, restoring the special to its best possible visual and audio incarnation. Rejoice that the mix and mastering on both the digital and vinyl versions are of such sterling sonic quality. And, rejoice, of course, Zappa fans, that the grail can finally be yours.