Simm was born in Birmingham and started playing the piano aged five, primarily self-taught he progressed quickly and by the age of eleven was playing regular local gigs. He also took up the trumpet and was later approached by David Hinds of Steel Pulse to play on and arrange horns for their Grammy Award nominated album, Victims.

Aged twenty Simm moved to London continuing work as a session musician, and also working as a sound engineer at various studios in London. He has played alongside Carleen Anderson, Pops Staples, Mica Paris, Baby D, Charles & Eddie and MC Solar.

At twenty seven, Simm stopped touring to concentrate on studio work. He worked on All Saints' debut album and went on to co-write and produce tracks for the Sugababes, including their BRIT Award nominated debut single Overload, which peaked at number 6 on the UK Singles Chart. Simm co-wrote Siobhán Donaghy's top 20 debut single Overrated and has written and/or produced tracks for Amy Winehouse, Neneh Cherry, Mutya Buena, Leon Jean-Marie, Groove Armada and Tom Jones.

In 2002, Simm along with co-writers McVey, Lipsey and Howard was awarded writing credits by ASCAP for the song Make Over, which appeared on Christina Aguilera's Stripped. The track was originally listed as having been written by Aguilera and Linda Perry, but critics claimed that it had borrowed heavily from the Sugababes' song Overload.

In 2005 Simm was commissioned to compose music for Gucci's Gucci pour Homme II campaign.