Green’s Dictionary of Slang

1. (US, orig. jazz) of both music and places, rough, tough, unpretentious music that started off in the repertoire of the musicians who played for cheap saloons.

1882		Nat. Police Gaz. (NY) 4 Nov. 2/4: They disappeared, to slow music, in the direction of a barrel-house saloon.
1937		H. Brook Webb ‘The Sl. of Jazz’ in AS XII:3 182: barrelhouse. Chiefly used to describe piano playing in that style developed by the ‘professors’ who play in the bordellos of Memphis, St Louis and New Orleans.
1944		Cab Calloway New Hepsters Dict. in Calloway (1976) 253: barrelhouse (adj.): free and easy.
1946		Mezzrow & Wolfe Really the Blues 136: Give me a barrelhouse joint on the South Side anyday [...] compared to the social life in the Rockies.
1967		L. Bruce Essential Lenny Bruce 28: Give me some full music — anything, barrelhouse.
1971		(con. 1910s) G.M. Foster Pops Foster 31: They only sold it in the Italian barrelhouse joints.
1971		(con. 1930s–50s) D. Wells Night People 117: Barrelhouse. lowdown and ornery.

2. used as adv.

1939

N. Algren ‘Lightless Room’ in Entrapment (2009) 44: Barrelhouse drunk and cussing out everyone walking past him.