The UMC's was a short lived New York-based rap duo, comprised of members Hass G and Kool Kim. The duo issued a pair of releases during their brief career -- 1991's self-titled debut and 1994's Unleashed -- but their lighthearted subject matter seemed out of place during an era when gangster rap ruled the charts, leading to the UMC's split shortly thereafter.
Source: http://www.allmusic.com/artist/the-umcs-p15208/biography
