Over the years, ISB members have made a number of guest appearances on other artist's albums. These are detailed here.
Both Robin and Mike make uncredited guest appearances on Scottish folk singer Hamish Imlach's self titled debut LP. Robin's vocals are clearly audible on 'The Zoological Gardens' and 'If It Wasn't For The Unions', and it's possible Mike may also be singing on the later. The mandolin playing on various tracks could well be Robin too.
Robin plays mandolin, guitar and adds backing vocals to many of the songs on Scottish folk singer Matt McGinn's self titled debut LP.
Mike 'plays Indian finger-cymbals and thumps an African drum' and Robin 'clicks Japanese sticks and plays tin whistle' on 'Richie Story'. 'Seven Yellow Gipsies' has 'two handsome gipsies (Robin Williamson and Mike Heron) clapping her on' and Robin 'adds his chanter (the Indian Shahanhai)' to 'The Maydens Came'. Shirley, along with her sister Dolly, went on to record Robin's 'God Dog' on the 1969 'Anthems In Eden' LP, and is also believed to have performed a medley of the ISB's 'Painting Box' and 'My Name Is Death' at a live show at the Liverpool Philharmonic Hall in the late 60s or early 70s.
Clive Palmer plays banjo and kazoo on Hamish Imlach's 1968 LP 'The Two Sides Of Hamish Imlach', and actually arranged several of the songs too. The album also features the track 'Clive's Song', a minor key blues credited to Clive, although Clive himself does not remember anything about the it.
Robin plays fiddle, mandolin and Irish harp on the songs 'Lily Pond', 'Rose Hip November' and 'Jog Along Bess' on Vashti's 1970 Joe Boyd-produced LP 'Just Another Diamond Day'.
Both Robin and Mike made guest appearances at Melanie's concert at the Theatre Royal, Drury Lane, London on 23.06.74, from which 'Chart Song' on her 1974 'As I See It Now' LP is taken. Mike plays Moog, acoustic guitar and contributes background vocals, whilst Robin adds kalimba. Mike's distinctive vocals are also heard on the studio recordings 'Eyes Of Man' and 'Don't Think Twice, It's Alright' on this LP, these songs being recorded at the same sessions as 'Evie' and 'Meanwhile The Rain' from the 'Mike Heron's Reputation' LP (on which Melanie guests). On these studio tracks, Robin may well have provided some of the musical backing and former ISB manager, and partner of Mike at the time, Susie Watson Taylor is also credited with providing backing vocals. Although not included on the LP, the Theatre Royal show, which was recorded by Capital Radio, also included a song Mike wrote especially for the evening, 'Do It Yourself (Desert Song)' (later heard on the Heron LP 'Diamond Of Dreams'). Melanie also recorded a studio version of 'Desert Song', featuring Mike on backing vocals, but this remains unreleased.
Robin plays mandolin on the song 'Raindance' on Melanie's 1976 LP 'Photograph'.
Robin plays oud on the song 'Bayou Eyes' on Jimmy Spheeris' 1976 LP 'Ports Of The Heart'. The album is dedicated to L. Ron Hubbard, which is presumably how he came to play on it.
An ISB guest appearance on an ISB member's album. Five years after mysteriously leaving the ISB, Licorice makes her last known recording on the Merry Band's 1977 debut LP 'Journey's Edge' along with her then husband Brian Lambert. She is credited as Likki (McKechnie) Lambert and provides her distinctive vocals to the songs 'Tomorrow' and 'The Bells'.
Robin plays penny whistle on the songs 'Troubadours' and 'Rolling Hills' on Van Morrison's 1979 LP 'Into The Music'. Van later returned the favour by recording Robin's 'For Mr Thomas' as the B-side of his 1983 'Celtic Swing' single (available on the 1998 'The Philosopher's Stone' compilation).
Malcolm Le Maistre co-wrote and provides lead vocals to the Enid's 1980 single 'Fool'. The B-side, 'Tito', has no apparent involvement from Malcolm.
Robin plays guitar on David Gates' 1980 LP 'Falling In Love Again'.
Robin plays mandocello on the song 'Rocks On The Ocean' on Al Stewart's 1980 LP '24 Carrots', which also features both Sylvia Woods and Jerry MacMillan from the Merry Band. Al has also said that the song 'Merlin's Time' from this LP is about Robin, although Robin denies this.
Robin plays penny whistle on Peter Alsop's 1981 LP 'Uniforms'.
Robin apparently appears on Iruka's 1982 LP 'Waga Kororo no Tomo-e', though no further information at the moment on what his contribution was.
Robin plays Celtic harp and bagpipes on James Horner's soundtrack to the 1988 film 'Willow'.
Robin contributes pipes and vocals to Welsh band Mabsant's 1989 cassette only release 'Cofeb'.
Robin plays Celtic harp, penny whistle and acoustic guitar on the former Dexy's Mignight Runners fiddle player Helen O'Hara's 1990 LP 'Romanza' (reissued as 'Southern Hearts').
Robin appears on two songs on his friend David Nigel Lloyd's 2008 album 'Rivers, Kings And Curses'. He plays Hardanger fiddle and fiddle on 'The Son Of Old Rosin The Bow' and harp on 'Will Ye No Come Back Again?'.