piano, v. — Green’s Dictionary of Slang

piano v.

[? one’s hands are tapping at the floor in the hope of feeling a tiny piece]

(drugs) to search on hands and knees for any small pieces of crack cocaine that may have fallen to the floor.

1992		T. Williams Crackhouse 150: pianoing using the fingers to find lost crack-cocaine or freebase.
2001		ONDCP Street Terms 17: Pianoing — Using the fingers to find lost crack.