Question: What British Canterbury scene signer was a guest musician on The Civil Surface?

Context paragraphs:
The Wilde Flowers: The Wilde Flowers were the archetypal Canterbury scene music group based in the vicinity of Canterbury, England.

Barbara Gaskin: Barbara Gaskin (born 5 June 1950) is a British Canterbury scene singer.

The Battle of Hastings (album): The Battle of Hastings is the 1995 album released by the British Canterbury scene progressive rock band Caravan.

Caravan (band): Caravan are an English band from the Canterbury area, founded by former Wilde Flowers members David Sinclair, Richard Sinclair, Pye Hastings and Richard Coughlan in 1968.  The band have never achieved the great commercial success that was widely predicted for them at the beginning of their career, but are nevertheless considered a key part of the Canterbury scene, blending psychedelic rock, jazz and classical influences to create a distinctive progressive rock sound.

Matching Mole's Little Red Record: Matching Mole's Little Red Record (1972) is the second album of the English Canterbury Scene band Matching Mole.  The band was formed in 1971 by Robert Wyatt after he left Soft Machine.  Compared to their first album, Little Red Record was more of a team effort, with Wyatt taking a less involved role.  It was produced by Robert Fripp of King Crimson, and features Brian Eno as a guest musician.

The Civil Surface: The Civil Surface is Egg’s third and final studio album, originally released in 1974 on Caroline Records.  The band had broken up in 1972, leaving some of their favourite stage pieces unrecorded.  At organist Dave Stewart's suggestion, the trio re-united in order to record these compositions.  Among the guest musicians on the album are Steve Hillage (guitar), Lindsay Cooper (oboe & bassoon) and vocalists Amanda Parsons, Ann Rosenthal and Barbara Gaskin.

Caravan (Caravan album): Caravan is the debut album by the British Canterbury scene progressive rock band Caravan.  It was released in January 1969.

Pye Hastings: Julian Frederick Gordon 'Pye' Hastings (born 21 January 1947 in Tomnavoulin, Banffshire, Scotland) is a British musician.  Born in Scotland and raised in Canterbury, Kent, he is the guitarist and vocalist of the Canterbury scene band Caravan and brother of Jimmy Hastings.

Canterbury scene: The Canterbury scene (or Canterbury Sound) is a subgenre of, or sibling to, progressive rock.  The term describes a loosely defined style of music created by a number of improvisational musicians, some of whom were based in the city of Canterbury, Kent, England during the late 1960s and early 1970s.

Romantic Warriors III: Canterbury Tales: Romantic Warriors III: Canterbury Tales (2015) is the third in a series of feature-length documentaries about Progressive rock written and directed by Adele Schmidt and José Zegarra Holder.  This one focuses on the music of the Canterbury scene.

Supporting paragraphs: The Civil Surface Barbara Gaskin
Answer: Barbara Gaskin