Green’s Dictionary of Slang

(Ling. Fr./Polari) a musical instrument, esp. a portable harmonium or a piano; thus striller a musician, a piece of music; strill-homey/polone, a male or female pianist.

1984		Partridge DSUE (8th edn) 1167/2: strill [...] 2. A piano [...] Hence, strill homey or strill polone, a pianist male or female [...] 3. A portable harmonium, esp. among pierrots [...] late C.19–20.
2019		P. Baker Fabulosa 298/1: striller(s), strill(s) 1. a musical instrument, 2. piano keys. 3. a musician [...] strillers omee noun: a pianist or musician.
2023		R. Milward Man-Eating Typewriter 19: The Hindi-strillers let loose a hypnotic raga [ibid.] 273: The bass and twang-striller slinked out of the speakers.