Green’s Dictionary of Slang

1. (UK Und.) a singer [meton.].

1859		Matsell Vocabulum.
1895		C. Crowe Aus. Sl. Dict. 53: Note, a singer.

2. (US) a joke [? it ‘strikes a chord’ in the hearer].

1891		J. Maitland Amer. Sl. Dict.
1911		C.E. Mulford Bar-20 Days 220: ‘Ain’t that a hell of a note?’ he demanded plaintively.
1940		O. Strange Sudden Takes the Trail 14: Helluva note, ringin’ in a perishin’ tramp.