One of the all-time greatest folk- & progressive-rock bands, and a true "fusion" band in every sense of the word was - and still is - Jethro Tull.
The outfit that was (& still is) led by Ian Anderson (foreground, at left) since its inception in 1967 went through rather numerous personnel-changes over the years, and despite all those changes the band has only had two electric lead guitarists (Anderson is quite proficient on acoustic guitar & harmonica as well as vocals & flute) in its entire history: of course there's Martin Barre (who joined Tull in '69 right at the cusp of their ascent to prog-rock success, and remains with Tull to this day) - but before Barre, there was a more blues- & jazz-centric guitar-manster - his name is Mick Abrahams.
Abrahams (born April 7, 1943 in Luton, Bedfordshire, UK) was already an established guitarist in the 60's British blues scene by the time he & drummer Clive Bunker (both worked together in the previous band they were in) joined Jethro Tull in early '68. Jethro Tull at the time was struggling to get gigs (oftentimes they would get bookings under different band-names) but once Abrahams & Bunker joined Anderson & bassist Glenn Cornick, the band started to take off (albeit in a more blues-oriented direction at the time) and that led to Tull's debut album This Was (and the only LP with Abrahams - it was named as such because by the time before it was released Abrahams had already left the band, so Anderson suggested the title). It's a fine & versatile album, despite what little sales it may have generated at the time of its release, but it got Jethro Tull's foot in the door, so to speak, and with the addition of Martin Barre in '69 the rest, as they say, is history.
The most noted reason for Mick's departure from Tull was that there was a clash between Mick and Ian on which direction to take Tull - Mick wanted to stay in the blues realm while Ian wanted the band to expand to a more varied - and more progressive, and thusly more commercially-viable - direction, which is exactly what Anderson did when he replaced Abrahams with Barre. Nonetheless, Mick soldiered on after Tull with Blodwyn Pig (left) and his own self-named band in the 70's and beyond.
Mick is still a working guitarist and bandleader to this day. Now in his 70's, though he's been slowed up recently by a heart-attack in 2009, and a more recent diagnosis with Ménière's disease (I have it too; it can be a nuisance at times but not too bad as long as you wear proper ear-protection at gigs), he is regaining his health somewhat and hopes to be more active on the UK club & festival scene soon. More power to ya, mah brother!
Check out Mick's official website, Squirrel Music!