Holmes was bass-player with the late-1980s Welsh language punk band Y Fflaps. After his bass amplifier blew up on stage, he moved to guitar and the band morphed into the more psychedelic Ectogram in 1993.
Holmes has worked as a session musician on several albums by Welsh artists including the debut album by Melys, and has produced several albums including the early releases of Gorky's Zygotic Mynci. He has also been responsible for much of the sleeve art of the Ankst label.
He continues to work with Ectogram, and has released several records as The Groceries.
The Welsh Alan Holmes should not be confused with another musician of the same name who was a prominent session saxophonist in the 1960s.