A plush box of the seven albums Cobham cut in a flourish of creativity following his days with the Mahavishnu Orchestra. There are few extras, just outtakes of album tracks, plus the singles, so there's no new insight. But then we're not talking Bitches Brew here. But, as Cobham shared with this correspondent, this is essentially simple music (which is not to disparage it) but played with a high musicianship, fiery passion and a desire to hit a compelling groove. And Spectrum hits the spot in all those respects. Indeed, so successful is its mix of rock attack, thanks mainly to Bolin, and jazz textures (the addition of Carter and Farrell lifts the whole project), that Cobham still fills concert halls with it 40 years on. Crosswinds develops similar themes, but now with a funk edge, thanks to the Breckers, and with a greater confidence, partially lent by Duke's keys. A Funky Thide of Sings hits the dancefloor hard – which Ellington wouldn't oppose – with its reminder that disco was all pervading at the time, and not necessarily detrimentally. The live albums, notably Shabazz, remind you of the band's visceral power and Cobham's untiring velocity. If the ideas are running thin by Inner Conflicts, you can't blame Cobham who'd gone through a punishing recording and live schedule. But by now he'd made his mark as an all round musician, not just the propulsive energy on the drum stool. The time for pastures new was beckoning

Jazzwise spoke to Billy Cobham about the album

How did Spectrum emerge from Mahavishnu?

This was music that came out of love, but also out of desperation! I had a lot of options: I was playing with Freddie Hubbard, Airto (Moreira), Flora (Purim), Don Sebesky. I'd had conversations with Columbia and needed to make a demo. I didn't see these guys, Sklar, Bolin, Jan (Hammer) as the band but I was desperate to pull something together from the momentum that was Mahavishnu.

Now you had the chance to be a composer and arranger?

I'd wanted to write (for Mahavishnu), but John McLaughlin wasn't interested so that shot a hole in that. Back then nobody looked at drummers as musicians. The perception hasn't changed much!

But you had inspiration?

Louie Bellson will always be my role model as a percussionist and composer. Bill Potts’ The Jazz Soul of Porgy and Bess, fantastic, but my biggest influence was Gil Evans, especially his work with Miles.

And with Crosswinds you had George Duke on board?

Yeah, there was a period I wanted to lock in with him. He was such a positive person, on the outside, but as I got closer to him, I saw he had serious eyes. I was exposed to the LA music scene through George. That LA scene was about politics, about who was scratching whose back. But NY was about musicianship; if you could play, you got work. The East was head and hands above the West, and I'll stand by that.

And with A Funky Thide… disco is making its mark?

Yeah, disco: that disco drumming was like listening to Thumper the rabbit, banging his tail, bang, bang, bang. That's how come I went out to Switzerland, 25 years ago, for the space, the quiet and the opportunity to work in ways I wanted. The key as an artist is to get the platform to perform, to state your musical case. You can't wait for someone else to butter your bread.