There are multiple artists using the name "Gamma".
1) Gamma is a band formed by guitarist Ronnie Montrose back in the 70s, after his band Montrose released several LPs, including the classic Montrose/Montrose(Bad Motor Scooter, Rock The Nation). From Northern California, Gamma received relatively little airplay even though their music was very high-quality with stellar musicianship and songwriting.
2) Gamma is a UK Hip-Hop crew on the label Big Dada. Read more on Last.fm