Kenan Bell is a genius. A big, integral part of hip-hop is using music that has often gone before as a canvass for one's own poetry. Kenan understands this very well - better than most - and has often used music that is definitely not typically affiliated with rap and hip-hop. The backdrop for this song was Moondog's 1969 song "Stamping Ground." And yes, this song was used in The Big Lebowski.
Just for fun, here is the original song he used:
Great stuff, Kenan. It's great to have you as a friend.