Crux of the Biscuit, new archival release from Zappa Records and Universal Music takes a dive into Frank Zappa’s most fertile period, showing how one of his best records came together from jam sessions and tightly-scripted compositions. It’s almost like a making-of documentary and for fans, it’s a welcome treat.

Generally, the mid-70s are seen as Frank Zappa’s high-water mark. Between 1973-75, he had his best sales, released a solid run of records and toured constantly with a steady core of talented musicians who left their thumbprints all over his music: Jean-Luc Ponty, George Duke and Chester Thompson, not to mention a cameo by Jack Bruce.

Originally, Apostrophe a big of a grab bag. The first side was the mostly the long “Don’t Eat the Yellow Snow” suite of connected songs, the other was series of unreleated jazz-rock. The first half yielded Zappa his biggest hit, but the second had some of his most memorable tunes: the slow R&B of “Uncle Remus,” the driving jazz-rock of “Apostrophe,” and the frantic experimentalism of “Excentrifugal Forz.” More to the point, it’s lacking the cynicism of Zappa’s later records, but isn’t as experimental as his earlier ones. In late June 1974, Apostrophe peaked at 10 on the Billboard charts, ahead of records by Grand Funk Railroad, Chicago and David Bowie.

Crux of the Biscuit focuses on this period, first offering early mixes of album tracks, then taking the listener through raw backing tracks, alternate takes and even a live, 20-minute performance of the “Yellow Snow” suite. It’s an interesting making-of, showing a familiar record at various stages of completion.

It opens with an early version of side one, featuring extended versions of “Cosmik Debris,” “Uncle Remus” and “Apostrophe,” plus an alternate mix of “Down in De Dew.” Of these, “Uncle Remus,” is the most interesting: it’s longer and has some tasty keyboard soloing by Duke. Meanwhile “Cosmik Debris” is largely the same: there’s a few seconds added, but it’s essentially the same as the released version.

The title track, however, is an interesting listen even if it’s too much of a good thing. The original version was built out of a jam session between Zappa, bassist Jack Bruce and a few session players. Each get a chance to stretch out and solo – there’s even a nice drum break by Jim Gordon – and it leaves you wanting more. The early version goes on and on, admittedly wandering at times. It’s nice to have, though.

From here, Crux of the Biscuit goes into documentary mode, featuring raw alternate takes, excerpts from an interview and a lengthy section of the Bruce/Zappa jam session. Confusingly, they’re all titled “Energy Frontier.”

The first two included versions (Takes Four and Six, if you’re keeping score) are alternates of “Down in De Dew,” featuring an unnamed flutist and a drastically different mix: the drums are way out in front and Zappa’s guitar isn’t as prevalent. The flute’s an interesting wrinkle, but neither will make listeners forget the original.

Next” is an eight-minute excerpt of the jam session edited down as “Apostrophe.” It’s interesting to hear them coming up the song’s signature riff as a group: it’s like you’re right there in the room with them. At the same time, it’s a jam session. Sometimes everything clicks, but sometimes Bruce and Zappa circle each other while Gordon and guitarist Tony Duran keep a groove going. For Zappa fanatics it’s gold, but I’m not as sure it’ll work for the casual fan.

The same goes for the basic tracks of the “Yellow Snow” suite: they’re interesting, but not essential. However, the instrumental version of “Cosmik Debris” shows off how tight his band was and his chops as a composer: even sans lyrics, the song works as a bluesy instrumental with his searing guitar leads and Duke’s melodic electric piano.

Finally there’s the lengthy live version of “Yellow Snow” recorded live in Australia in 1973 (don’t worry die-hards: it’s from a different show than the live version on One Shot Deal). It’s fun and interesting to hear them twist and turn through this song. One moment Ruth Underwood’s taking a marimba solo then the rhythm suddenly to a slow blues, only to flip into a quick Latin rhythm. That his band was able to make these flips, night after night on the road, as one continuous performance is impressive.

Which is maybe the best way to sum up Crux of the Biscuit. It’s impressive because it shows his band’s talent, but also because it expands on Apostrophe, shining a light on how it started and how it sounded on stage. If you’re unfamiliar, start with Apostrophe before going here; but if you’re already a fan, you’ll love this.