He is best known for his harmonica feature performance on the Northern Exposure tv series theme and on recordings by artists including Christopher Cross, Al Jarreau, Earth Wind and Fire, Natalie Cole, Gino Vannelli, Dave Grusin, and Billy Idol among others and his live performance with major touring artists.

Around the same time he started gaining notoriety as a session harmonica player, starting with being featured in the theme for the television series Northern Exposure, and then a series of live credits with artists such as Don Henley, Andrea Bocelli, Chet Atkins and Kenny Loggins as well as features on several artist's albums including Al Jarreau, Earth Wind and Fire, Natalie Cole, Gino Vannelli, Christopher Cross, Dave Grusin, Don Grusin, Billy Idol, M83 and Brian McKnight.

[4] As a keyboardist/vocalist he has additionally toured or performed live with other artists including Michael McDonald, Kenny Loggins, Sheena Easton, Jewel, Edgar Winter, Al Stewart, David Becker, and Seal.

[8] Ollestad has also released three albums of original music independently, respectively "Walk the Earth" 2004, "Across the Rubicon" 2009 and "Tollak live" 2016.

[11][12] He moved to the Netherlands in 2004 where he currently resides and continues to perform, record and teach, as well as elsewhere in Europe, America and other venues worldwide.