Joe Strummer & the Mescaleros

Many of the band members were multi-instrumentalists. The original line up consisted of Strummer on vocals and guitar; Antony Genn on guitar; Scott Shields on bass, guitar and drums; Martin Slattery on keyboards, guitar, occasional flute and saxophone; Pablo Cook on percussion; Steve "Smiley" Barnard on drums; and Richard Flack on various instruments.

The Mescaleros arose from Strummer's work with Pablo Cook and Richard Norris. The three of them originally came together to write the soundtracks for two short films, Tunnel of Love, and Question of Honour. The song "Yalla Yalla" was originally written by this trio, and mixed by Antony Genn. Once Genn was brought on board, a new song "Techno D-Day" was recorded, at which point Strummer, at the behest of Genn, began recording a new record.
The original drummer, Ged Lynch, left the band before recording on the Rock Art and the X-Ray Style album was complete and Steve Barnard, previously with Robbie Williams, was brought in to finish recording. Shields and Slattery were recruited through a number of contacts with the band. Slattery had also appeared on Williams' Life thru a Lens album, and Shields was a friend of Slattery's. Oddly enough, in the initial lineup, only Smiley was playing the instrument which he knew best.
Genn reportedly did not have the ability to play sufficient lead guitar, so multi-instrumentalist Slattery, originally trained on horns and keyboards, was brought in. Strummer once joked that Slattery could play a hole in the windshield of the tour bus. Shields had previously been a drummer but was recruited to play bass, and later played guitar.