One for the treble, two for the bass
Come on Jam Master, let's rock the place

from Run-D.M.C. (Ft. Kool Moe Dee & Special K) – "Graffiti Rock" Freestyle Lyrics on Rap Genius

Meaning

This “one for the treble” opening is a nod to the simple but effective party chants that would be done at Bronx parties in hip-hop’s early days by rappers such as Coke LaRock

The “Jam Master” here is, of course, Run-D.M.C.’s Jam-Master Jay

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