Green’s Dictionary of Slang

(US black) a spontaneously assembled musical group, playing on homemade instruments (washtubs, washboards etc); the precursors of the skiffle groups of the 1950s.

1936		Kingston Dly Freeman (NY) 29 Feb. 7/3: Lacoume has spent most of his life at music after organizing his own ‘spasm band’ of newsboys with homemade instruments.
1941		(con. 1900s) A. Lomax Mister Jelly Roll (1952) 61: Also a lot of bands that we used to call ‘spasm bands’, played any jobs they could get in the streets.
1956		Gautier & Panassie Guide to Jazz n.p.: spasm band: small street band, the instruments of which are objects not usually used for making music, e.g., suitcase for drums, wine jug for tuba, etc. Flourished when jazz was simpler, more primitive.
1963		J. Rechy City of Night 322: Dixieland bands become more numerous. Spasm bands sprout.
1986		(con. c.1920) D. Barker Life in Jazz 35: There were many spasm bands in the city. They played [...] musical saws, washboards, spoons, bells, pipes, sandpaper, xylophones, sets of bottles (each with a different amount of water), harmonicas, jews harps, one-string fiddles, guitars, small bass fiddles, tub basses, kazoos, ram horns, steer horns, bugles, tin flutes, trombones, and many others.