He worked as a freelance session drummer on records and tours for the following artists: Incognito, Lisa Stansfield, Lewis Taylor, Artful Dodger, Paul Young, Iggy Pop, Level 42, Porcupine Tree, OSI, King Crimson, Shooter, Dizrhythmia, The Pineapple Thief, The Kings Of Oblivion, Sam Brown, Tom Robinson, Go West, Black, Gail Ann Dorsey, B.J.

Cole, Dave Stewart and Barbara Gaskin, Nathan East, Yasuaki Shimizu, Camouflage, Kevin Ayers, Claudio Baglioni, Franco Battiato, Chizuko Yoshihiro, Renaissance, Mick Karn, Eros Ramazzotti, Nick Johnston, Randy Goodrum, and Fates Warning.

On 23 August 2011, he was a featured performer on the 'Late Show with David Letterman' as part of their second "Drum Solo Week", along with such players as Sheila E, Stewart Copeland, Neil Peart, and Dennis Chambers.

In 2016, he joined The Pineapple Thief as a session drummer for the band's 11th studio album Your Wilderness, which received widespread critical acclaim and an overwhelmingly positive fan reception.

Many artists have cited Harrison as an influence, including Chad Szeliga, Chris Pennie,[5] Ryan Van Poederooyen,[6] Dirk Verbeuren,[7] Andrew Spence,[8] Raymond Hearne of Haken,[9] John Merryman of Cephalic Carnage,[10] Jamie Saint Merat of Ulcerate,[11] Aaron Stechauner of Rings of Saturn,[12] Baard Kolstad of Leprous,[13] Francesco Paoli of Fleshgod Apocalypse,[14] Matija Dagović of Consecration,[15] Vishnu Reddy of Crypted and Abhay Rathore (former Mocaine).

[16] In addition, other artists have been quoted expressing admiration for his work including Neil Peart,[17] Bill Bruford,[18] Mike Portnoy,[19] Devin Townsend,[20] Steve Smith,[21] Martín López,[22] Matt Garstka,[23] Dave Bainbridge,[24] Hannes Grossmann,[25] Blake Richardson,[26] Kai Hahto,[27] Jimmy Keegan,[9] Ian Mosley,[28] Dan Presland of Ne Obliviscaris,[29] Evan Sammons of Last Chance to Reason,[30] Bodo Stricker of Callejon,[31] Joshua Theriot of Abigail's Ghost,[32] and Blake Anderson of Vektor.