Green’s Dictionary of Slang

(Aus./n.Z. drugs/prison) a hypodermic syringe; thus play the violin v., to inject oneself.

1990		Tupper & Wortley Aus. Prison Sl. Gloss. 🌐 Violin. A syringe. As in ‘to play the violin.’.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 198/1: violin, the n. a hypodermic syringe.