The Incredible String Band (sometimes abbreviated as ISB) were a psychedelic folk band formed by Clive Palmer, Robin Williamson and Mike Heron in Scotland in 1966. The band built a considerable following, especially in the British counterculture, notably with their albums The 5000 Spirits or the Layers of the Onion, The Hangman's Beautiful Daughter, and Wee Tam and the Big Huge. They became pioneers in psychedelic folk and, through integrating a wide variety of traditional music forms and instruments, in the development of world music. Following Palmer's early departure, Williamson and Heron performed as a duo, later augmented by other musicians.

1968 was the band's annus mirabilis with the release of their two most-celebrated albums, The Hangman's Beautiful Daughter and the double LP Wee Tam and the Big Huge (issued as two separate albums in the US). Hangman's reached the top 5 in the UK album charts soon after its release in March 1968 and was nominated for a Grammy in the US. Robert Plant of Led Zeppelin said his group found their way by playing Hangman's and following the instructions. A departure from the band's previous albums, the set relied heavily on a more layered production, with imaginative use of the then new multitrack recording techniques. The album featured a series of vividly dreamlike Williamson songs, such as "The Minotaur's Song", a surreal music-hall parody told from the point of view of the mythical beast, and its centrepiece was Heron's "A Very Cellular Song", a 13-minute reflection on life, love and amoebas, its complex structure incorporating a Bahamian spiritual ("I Bid You Goodnight"). Williamson and Heron in this album had added their girlfriends, Licorice McKechnie and Rose Simpson, to the band to contribute additional vocals and various instruments, including organ, guitar and percussion. Despite their initially rudimentary skills, Simpson swiftly became a proficient bass guitarist, and some of McKechnie's songs were recorded by the band.  By early 1968 the group were capable of filling major venues in the UK. They left behind their folk club origins and embarked on a nationwide tour incorporating a critically acclaimed appearance at the London Royal Festival Hall. Later in the year they performed at the Royal Albert Hall, at open-air festivals, and at prestigious rock venues, such as the Fillmore auditoriums in San Francisco and New York. After their appearance at the Fillmore East in New York they were introduced to the practice of Scientology by David Simons (aka "Rex Rakish" and "Bruno Wolfe", once of Jim Kweskin's Jug Band). Joe Boyd, in his book White Bicycles: Making Music in the 1960s and elsewhere, described how he was inadvertently responsible for their "conversion" when he introduced the band to Simons, who, having become a Scientologist, persuaded them to enrol in his absence. The band's support for Scientology over the next few years was controversial among some fans and seemed to coincide with what many saw as the beginning of a decline in the quality of their work. In an interview with Oz magazine in 1969 the band spoke enthusiastically of their involvement with it, although the question of its effect on their later albums has provoked much discussion ever since.  Their November 1968 album Wee Tam and the Big Huge, recorded before the US trip, was musically less experimental and lush than Hangman's but conceptually even more avant-garde, a full-on engagement with the themes of mythology, religion, awareness and identity. Williamson's otherworldly songs and vision dominate the album, though Heron's more grounded tracks are also among his very best, and the contrast between the two perspectives gives the record its uniquely dynamic interplay between a sensual experience of life and a quest for metaphysical meaning. The record was released as a double album and also simultaneously as two separate LPs, a strategy which lessened its impact on the charts.

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1968 was the band's annus mirabilis with the release of their two most-celebrated albums, The Hangman's Beautiful Daughter and the double LP Wee Tam and the Big Huge (