Main Source is an innovative, acclaimed Toronto and New York-based hip hop, group comprised of Toronto natives Sir Scratch, K-Cut, and New York-native Large Professor.

Their first album, Breaking Atoms, featured conscious MC tracks such as "Looking at the Front Door" and "A Friendly Game of Baseball" and "Watch Roger Do His Thing" as well as the first on-record appearance of Nas on "Live at the Barbeque", which also featured Joe Fatal and Akinyele. Because of business differences, the group broke up before their second album, tentatively entitled The Science could be released. However, Sir Scratch and K-Cut released a second album under the Main Source name, entitled Fuck What You Think, with new recruit Mikey D on vocals;however, the album was shelved due to inner conlficts between the record label and group management.

Large Professor has gone on to be an instrumental producer for hip-hop stars such as Eric B. & Rakim, Pete Rock and CL Smooth, Nas, and Diamond D. He has released a Solo LP entitled First Class, and his shelved The LP has been widely bootlegged.