By 1969, Johnstone had secured regular work as a session musician, where he began to branch out and explore differing genres of music, and experiment with a variety of instruments.

In 1970, when Lyell Tranter (one of the two guitarists in the acoustic British folk group Magna Carta) left the band, Johnstone took his place as a member.

In 1972 he worked with Joan Armatrading and Pam Nestor on their Gus Dudgeon-produced debut album Whatever's for Us, playing acoustic and electric guitar on several tracks, and sitar on the song "Visionary Mountains".

With music and lyric in place, the two formed Warpipes, which included past and present Elton John band members Nigel Olsson on drums, Bob Birch on bass, Guy Babylon on keyboards, along with Billy Trudel as vocalist.

Co-producer Guy Babylon joined with keyboard arrangements, alongside drummer Nigel Olsson and Billy Trudel adding percussion and vocals respectively.

[7] On 1 October 2019, Johnstone performed his 3,000th show with Elton John at the first of two Farewell Yellow Brick Road tour stops at the SaskTel Centre in Saskatoon, Saskatchewan.

King With Shaun Cassidy With Ryan Malcolm With Jimmy Webb With Rick Astley With Kiki Dee With Brian Cadd With Olivia Newton-John With Bernie Taupin With Rod Stewart With Yvonne Elliman With Vonda Shepard With Leo Sayer With Stevie Nicks