Guy Allison’s first record deal was signed with a band called Lodgic on A&M Records in 1985. This band included Michael Sherwood, Billy Sherwood, Jimmy Haun & Gary Starnes. The band was discovered by the 80's group Toto and was subsequently produced by Toto members David Paich and Steve Porcaro..

In 1987, Allison was selected by Patrick Moraz to fill the second keyboardist chair for the Moody Blues, a position he held until 1990. While touring with the Moodies he was a member of World Trade signed to Polygram Records. Recording their progressive self-titled debut album in 1988, this group included ex-Lodgic bandmate Billy Sherwood..

After the breakup of World Trade, Allison was tapped to join Air Supply in the recording studio and, ultimately on tour. This 7-year relationship generated 4 studio albums, Credited with co-writing 6 songs, 3 of these Allison/Russell co-compositions charted internationally.

During his time with Air Supply, he and ex-World Trade bandmate, Bruce Gowdy, formed the harder edge Unruly Child with singer Mark Free. Signed by Interscope Records, UC found cult status overseas yet remained undiscovered in the U.S.

After Unruly Child disbanded, Allison continued to tour with both Air Supply and also recorded an album with former Toto singer Bobby Kimball, titled “Rise Up”. He forged a musical relationship with some fellow touring members, John McFee and Keith Knudsen, which led to him joining The Doobie Brothers in 1996 as a touring keyboardist. Allison co-produced the Doobies' 12th studio album, 2000's Sibling Rivalry..

Allison released his debut solo album, A Designed Presence, in 2023.