Green’s Dictionary of Slang

piccolo n.

1. the penis.

1966		Trimble 5000 Adult Sex Words and Phrases.
1971		L. Sanders Pleasures of Helen 195: [S]he reached around and very slowly, very softly, very gently, grasped his piccolo.
1987		R. Campbell Alice in La-La Land (1999) 6: That there is Roberta Duckweiler, otherwise known as Bobby Ducky ever since she decided to have a cutter fashion her a piccolo and a pair of castanets.

In compounds

piccolo-player (n.)

a fellator or fellatrix.

1927		‘J.M. Hall’ Anecdota Americana I 6: ‘Who called my piccolo player a cock-sucker?’ he demanded. A voice in the rear of the theatre yelled back: ‘Who called that cock-sucker a piccolo player?’.
1966		Trimble 5000 Adult Sex Words and Phrases.
1972		B. Rodgers Queens’ Vernacular.
1989		J. Morton Lowspeak 111: Piccolo player – the active homosexual in fellatio. It can also refer to a prostitute who prefers to service clients in this way.
1990		Tupper & Wortley Aus. Prison Sl. Gloss. 🌐 Piccolo player. One who engages in fellatio.