Brought to us by part of the team who masterminded the excellent Jazz In Britain label, British Progressive Jazz is a new imprint with a similar mission: to unearth and release previously unheard sessions from the 1960s/70s golden age of UK jazz. Digital-only at present, there are plans for physical releases if sales are good. Judging by this first tranche, they certainly deserve to be.

The live set from 1971 by pianist John Taylor’s sextet is a dense half-hour with a gorgeously warm analogue sound, glowing with neon taxi-cab glamour like a drizzly night in Soho. Taylor’s ambitious and assured themes roam from the lightly skipping opening track (with a hint of Herbie Hancock’s ‘Maiden Voyage’), through episodes of dark, nocturnal swing and a more abstract, free-form interlude. His arrangements make the sextet sound like a much bigger ensemble, brilliantly balancing flute and trombone at either end of the palette, while Kenny Wheeler’s trumpet is both forceful and lyrical throughout. It’s an absolute gem.

There’s similarly rich material on another sextet session led by Don Rendell, a four-part, 29-minute suite that roars straight out of the gate with irrepressible joie de vivre as Rendell’s and Stan Robinson’s twin saxes entwine and Trevor Tomkins’ drums crash with glee, before settling into a relaxed, introspective mood with louche, velvety insouciance. Again, there’s enormous panache in the arrangements, with Rendell taking advantage of the group’s multi-instrumental skills that effectively swell the front line to two saxes, three flutes and vibraphone, with endlessly inventive support from pianist Michael Garrick. The term ‘progressive jazz’ could have been coined especially for this set.

Not surprisingly, there’s something of a big band feel to the live session featuring a 17-piece ensemble led by saxophonist John Dankworth. On tracks like the opener, ‘The Imaginary Mirror,’ it’s hard not to discern a 1970s light entertainment vibe but, when the show-biz arrangements thin out a little, there’s a hard-swinging unit at the core, featuring some energetically wide-screen drumming from Kenny Clare. There are some surprises too. ‘Orinoco’ is a deliciously slinky groove with low-down clavinet and nervous, paranoid horns, like Isaac Hayes scoring an Elstree Studios spy flick. The finale, ‘Earth Man,’ is a bongo-heavy rumbler with a spiky guitar solo from Chris Spedding and a neat flute solo from the great Stan Sulzman complete with Roland Kirk-style sub-vocalisations. A lot going on, for sure.

But if it’s quirky you’re after, direct your attention to the little-known Indo-Jazz session led by Indian violinist John Mayer, which reprises the heavily grooving, raga-inflected aesthetic of Mayer’s classic collaborations with Joe Harriott, this time with Sulzmann providing quicksilver alto saxophone. American harmonica player Larry Adler is the unlikely guest throughout, bringing his sweet and supremely tuneful precision to bear on Mayer’s compositions and, in more familiar territory, a rather melancholy rendition of Gershwin’s ‘Summertime.’ On paper, it shouldn’t work but, in practise, it’s a uniquely beguiling date. Who knows what other treasures the British Progressive Jazz label will uncover?