Spittin’ heat for 10 years and haven’t been signed once, says Pumpkinhead of his secure independent status. “Rock On” is P’s dedication to all underground artists, from Jean Grae to Mobb Deep, as he explicitly describes in tight verses over Marco Polo’s gritty beats. Based on the b-side track, “Swordfish,” I get the impression that P’s a confident live performer in the vein of Chubb Rock and Chuck D: loud, proud, lyrical and thoroughly hip-hop.