It's sometimes hard to imagine in today’s pop landscape, but back in the 1960s there was a definite insurrection happening in folk, a drawing of battle lines about what ‘folk music’ could be. The folk revival of the previous decade, full of reverence for tradition and purism, had fossilised into a dogma of conservatism. Many of the younger singers and musicians breaking through chafed against what they saw as a parochial and out-of-touch clique.

From this unrest rose a triumvirate of folk bands whose musical explorations played a part in causing folk music to slip its traditional shackles and become, in the words of Rob Young in his book on modern British folk music Electric Eden, a “floating signifier to be plucked from the air and appropriated by anyone who could find a suitable framework”. In one corner there was Fairport Convention, who grafted UK folk to a US country rock sound. In another, you had the likes of The Incredible String Band, whose hippy meanderings across north Africa and Asia resulted in strange instruments, new sounds and a positively kaleidoscopic freak scene of psychedelia.

But probably the most beguiling and inscrutable of them all is Pentangle. In the five-year period of the band’s main existence, between 1968-1972, they created a body of work that pretty much set the standard for the shapeshifting, experimental folk music that you can still hear today. The freewheeling journey they embarked through their six albums - The Pentangle, double LP Sweet Child, Basket Of Light, Cruel Sister, Reflection, and Solomon’s Seal - is now laid out in this sprawling retrospective collection, released by Cherry Red. There have been other collections of Pentangle’s music, most notably the 2007 compilation The Time Has Come 1967-1973, but The Albums seeks to provide the definitive statement of their corpus. Not only are the band’s five albums fully remastered, the retrospective also collects the bonus tracks that appeared on The Time Has Come and the 2001 reissues of the albums alongside previously unreleased outtakes and live performances, laid out in a roughly chronological pattern of the band’s genesis, rise and eventual dissipation.

When Pentangle officially came together in 1967, they had already known each other for several years, drifting together and apart within the sprawling UK folk scene. Guitarists Bert Jansch (then the high prince of folk guitarists) and John Renbourn had made an album together, 1966’s Bert and John, while singer Jacqui McShee appeared on Renbourn’s 1966 solo album, Another Monday. But they were definitely not folk purists; McShee cites jazz as her first true love, stumbling into folk by accident, while drummer Terry Cox and bassist Danny Thompson were hardened session pros and jazz aficionados who cut their teeth on the grinding UK jazz/blues circuit.

And it’s this divergent mixing of styles from jazz to blues that you can hear on the first disc, which contains Pentangle’s 1968 self-titled debut album (along with session outtakes). The album itself is a decidedly un-folk proposition, right from the cover shot, with the group depicted in 1960s modernist monochrome fashion - about as far from the epoch’s standards of folk album art as possible. On the record itself there are the pattering fills and scampering runs of Cox’s brushes on the snare, Thompson’s elastic virtuoso bass solos (how non-folky can you get!) and the grinding visceral sounds he pulls from his bowed bass on the folk standard ‘Let No Man Steal your Thyme’. Jansch and Renbourn display a surfeit of duelling bluesy chops and picked lines and solos that swoop across and over each other, such as on the climax to the band’s signature tune ‘Pentangling’; McShee’s vocals glide through the noise, her clean and pure register an antidote to the brooding and murky sounds. The Pentangle is an album that mirrors its time, bursting with energy and multiple ideas that shoot off in all directions, energising folk and blues standards such as ‘Bruton Town’ and ‘Hear My Call’ with a blaze of improvisation and an intuitive feeling for what works. In lesser hands, this would have been an incoherent mess, but the technical precision of the band keeps it all together. Out of the bonus tracks, the fingerpicking flurry of ‘The Wheel’ and the warm, smoky burr of ‘The Casbah’ are the definite standouts.

Discs 2, 3 and 4 contain Pentangle’s short burst of mass popularity, with the ambitious 1968 double album Sweet Child and the commercially successful Basket of Light from 1969, containing their best-known song ‘Light Flight’. To the band themselves, the first album in Sweet Child, a recording of their concert London’s Royal Festival Hall on 29 June 1968, stands as the truest statement of what Pentangle were about. A year of constant touring and balancing of individual egos had forged them into a formidable live proposition, tight and disciplined yet able to improvise and turn the direction of a song at will. For an ostensibly acoustic group, they fill the hall with an intimacy that is particularly intense as the music, especially in solo renditions such as ‘Haitian Fight Song’ (Thompson) and ‘So Early the Spring’ (McPhee) glow and reverberate the way a candle slowly illuminates the darkest room. They weren’t afraid to tear it up in a live setting, though - the live bonus track of ‘Pentangling’ contains a powerful, punchy groove set up by Cox and Thompson.

The studio albums of Sweet Child and Basket of Light expand upon their jazz and blues roots to explore folk traditions and early music (something that Renbourn was taking a special interest in at the time). It takes old arrangements such as ‘Soave’, ‘The Trees They Grow High’, ‘Cuckoo’ and especially “House Carpenter’ and leavens them with the vitality and creativity of their present-day, mixing the arrangements with banjos, the raga drones of sitar and a rumbling rhythm section.

With 1970’s Cruel Sister, contained here in CD 5, they go on an artistic and career swerve that seemed perverse to many at the time, a sign of the end of Pentangle’s time as pioneers. Morale in the band was low, with relationships strained to breaking point thanks to a gargantuan touring schedule and the pressures of recording (their propensity for drinking to smooth over the cracks did not help). When they went into the studio to make Cruel Sister, there was a retreat of sorts back to first principles; they dispensed with Shel Talmy, who had produced the first three albums, and brought in Bill Leader, who was known for producing the sparser DIY set-ups of the early folk revival recordings. The songs were reworkings of old folk standards instead of new compositions.

The result was a commercial and critical failure, but much as with Neil Young’s 70s albums, Cruel Sister eschews the need to be constantly striving outwards for the new and instead sees Pentangle in a more introspective mood, as they explore the dark, grim stains contained in these old songs with a sense of carefree ease. It is in this album that McShee comes to the fore. In tracks such as ‘A Maid Deep in Love’ and especially on the murder ballad ‘Cruel Sister’, her voice, contains little in the way of gaudiness or melodrama and is pricked with pain and the faintest quiver of emotion. Then there is recreation of their song ‘Jack Orion’ into a 20-minute epic poem odyssey, its wide-reaching but precise narrative rising and falling - and helping provide the blueprint for much of 70s prog rock.

By the time of their last two albums, 1971’s Reflection and 1972’s Solomon’s Seal, the journey for Pentangle was pretty much over. The band was now living in different parts of the country, the energy that had brought them together was spluttering out, and each of the members was threatening to quit on a regular basis. The fact that Reflection is as good an album as it is, is a testament to their individual talents and the patience of producer Lerner. Of the folk covers, a mix of Appalachian folk rock on ‘Wedding Dress’ and the mix of blues and country on the hymn ‘Will the Circle be Unbroken’ catch the ear, while Jansch’s song ‘When I Get Home’, a poem to the evergreen Saturday night/Sunday morning tribulations of hard living and overindulgence is a delightful mix of confession and regret. The final track, ‘Reflection’, has a dark, brooding jazz swing that shows the band were still far removed from those arran sweaters and beards of the folk purists. A slightly wanner situation is evident with Solomon’s Seal; the vibrance and vitality of their early albums is no longer evident.

Instead there’s a slightly more sombre, weary air and the sense that the members were looking out to other ventures. Both Jansch and Renbourn’s guitars had taken on an electric dimension, complete with wah-wah and a soft blues twang in their sound; songs like ‘Sally Free And Easy’, ‘People On The Highway’, and ‘Lady of Carlisle’, with drifting grooves and hazy quivering tones, sound like they could have been transplanted from the US West Coast. (This predilection for bluesy rock was not a new development: alongside the modern production rock groove of the bonus tracks ‘Faro Annie’ and ‘John’s Song (Take 5)’, earlier bonus tracks such as ‘Poison’ and the electric version of ‘Market Song’, the band were rocking out even in their early days.) And while the beauty in songs such as the folk standard ‘Willy O’ Winsbury’ is self-evident, there is something a bit comfortable about the proceedings, as if they were on cruise control. Indeed, Solomon’s Seal was supposed to have been the first of a multi-album deal for Pentangle with the Warners sub-label Reprise. Such was the acrimony in the band, they ended up cancelling scheduled sessions for the next album and split up days before getting hold of a guaranteed £5,000 for the album.

The question of “Why now?” may arise for those looking at the necessity of this box set. After all, there have been compilations and reissues of the band’s material in the past, and there is a limit to how many different versions of a song you can reasonably have on a CD. But, across all seven discs, the remastering efforts can’t go without comment. With a little reverb placed here and there and everything, including the onstage and studio banter, kept intact, the balance is very much restored between the various elements within the band. You can now hear, for example, how important Cox and Thompson’s efforts in the rhythm section were in providing the bedrock upon which the other band members were able to take off and explore to sometimes self-indulgent degrees. Listening to this boxset, you also begin to realise how much Pentangle were a product of their time, and how during that five-year period they were so creative, atmospheric and driven that you’d be hard-pressed to imagine any of their modern descendants achieving anything on this level, not for a long time to come.