What do both Andy Partridge and John Mayer do in their bands as well as writing songs and singing?
guitarist
Title: Andy Partridge
Passage: Andrew John Partridge (born 11 November 1953) is an English singer, songwriter, guitarist, and record producer who co-founded the rock band XTC.  He lives in Swindon, Wiltshire, where he was raised.
Title: John Mayer
Passage: John Clayton Mayer ( ; born October 16, 1977) is an American singer-songwriter, guitarist, and producer.  He was born in Bridgeport, Connecticut, and raised in nearby Fairfield.  He attended Berklee College of Music in Boston, but disenrolled and moved to Atlanta in 1997 with Clay Cook.  Together, they formed a short-lived two-man band called Lo-Fi Masters.  After their split, Mayer continued to play local clubs—refining his skills and gaining a following.  After his appearance at the 2001 South by Southwest Festival, he was signed to Aware Records, and then Columbia Records, which released his first EP, "Inside Wants Out".  His following two full-length albums—"Room for Squares" (2001) and "Heavier Things" (2003)—did well commercially, achieving multi-platinum status.  In 2003, he won the Grammy Award for Best Male Pop Vocal Performance for the single "Your Body Is a Wonderland".
Title: John Mayer Trio
Passage: The John Mayer Trio is an American blues rock band that formed in 2005.  Comprising singer-songwriter and guitarist John Mayer, bassist Pino Palladino and drummer Steve Jordan, the band has released one live album, "Try! " in 2005.  Three of the songs on the album were co-written by Jordan, Mayer, and Palladino, and the album was co-produced by Mayer and Jordan.
John Mayer Andy Partridge