Short answers, pulled from the story.
Large Professor, born William Paul Mitchell on the 21st of March, 1972, is an American rapper and record producer from Flushing, Queens. He is a founding member of the hip-hop group Main Source and is credited with having discovered and mentored Nas, producing three tracks on Nas's landmark 1994 debut Illmatic.
Large Professor produced three of the ten tracks on Illmatic: "Halftime", "One Time 4 Your Mind", and "It Ain't Hard to Tell". That total tied him with DJ Premier for the most production credits on the album. Nas offered him an executive producer credit, which he declined.
Main Source released Breaking Atoms in 1991. The album included tracks "Just Hangin' Out" and "Looking at the Front Door", and featured Nas's first public appearance on a track called "Live at the Barbeque" alongside Akinyele and Joe Fatal.
Large Professor completed The LP for Geffen Records in 1996, but the album was shelved after several delays. A bootleg version circulated in 2002, and an official release did not arrive until 2009, thirteen years after its original intended release date.
Large Professor's mentor Paul C taught him how to use the E-mu SP-1200 sampler. Paul C's influence extended to Large Professor's production work for Eric B. & Rakim; the track "In the Ghetto" was built from samples off a cassette of ideas that Paul C had originally made for Rakim.
Large Professor founded Main Source in 1989. The other members were K-Cut and Sir Scratch, both natives of Toronto. The group reunited for a concert in Toronto on the 22nd of December, 2002, their first performance together in nearly ten years.