Green’s Dictionary of Slang

harp n.2

[abbr. SE Jew’s harp]

1. (orig. US) a harmonica, a mouth organ.

[US]Scribner’s Mag. Oct. 481/1: She displayed a flimsy red silk handkerchief and a child’s harp .
[US]Ade ‘Why “Gondola” Was Put Away’ in In Babel 40: I’d walked from Loueyville over to Terry Hut with a nigger that played the mouth-harp.
[US]L. Bangs in Psychotic Reactions (1988) 104: I dropped the harp, which was such a limited palette for an experimental artist anyway.
[UK]J. Morton Lowspeak.
[UK]K. Richards Life 88: Cyril Davies was a hell of a harp player, one of the best.

2. (US) a vibraharp or vibraphone.

[US]Pic (N.Y.) Mar. 7: jibing the vibes or hitting the harps. — playing the vibraphone.