A harness is provided for securely holding a conventional plectrum or pick in firm engagement with a guitar player's thumb, the harness consisting of a flexible and resilient strap contoured to fit around the thumb in advance of the first knuckle and being provided with a central portion which is slit to receive and hold the plectrum firmly against the undersurface of the thumb with the pointed end of the pick protruding through one of the slits into playing position.