Depends on who that "average joe" was. People played much more music for their own pleasure than we do today; small towns did have "opera houses" -- which while they didn't often play Verdi, did have aspirations to European culture. So, for example, we have records that in 1877, an opera by Balfe, The Bohemian Girl, was performed at the Belvidere Theatre in Central City, Colorado. This today little known light opera seems to have been a favorite in the old West opera houses, along with The Mikado.
Consider the piano player-- he might be self taught, or he might be an Eastern swell who'd come out west, doing his Teddy Roosevelt. A remarkably diverse range of men and women sought adventure and fortune on the American frontier-- the French nobleman, the Marquis de Morès, a graduate of St Cyr (the French military academy-- he was a classmate of Petain)- came to the Dakotas to make a bundle in cattle ranching. He and his wealthy American wife would have been familiar with the "greatest hits" of contemporary European culture; you can say "he's not an 'average Joe", but . . .
What I'd say is: revisit your idea of who "average Joe" is in the "old West". He might be a former Confederate soldier. He might be a former slave. He might be a Chinese railroad worker. He might be British with a fancy title. He might be a Methodist who'd know all the verses of popular hymns but have no idea of Mozart. He might be a Mexican or South American working on ranches (essentially all of the ranching technology and terminology that we think of as "western" is Spanish in origin, that "buckaroo" is actually a vaquero) and playing guitar for himself and his friends.
Some of these people couldn't read . . . some of them could play Chopin. It's a very diverse crew, much more so than legend would have it.
sources:
Marquis De Mores: Dakota Capitalist, French Nationalist
Chateau de Mores State Historic Site
Prairie Fever: British Aristocrats in the American West, 1830–1890
Kwangtung to Big Sky: The Chinese in Montana, 1864-1900
Colorado's Historic Opera Houses
Spanish Influence in the United States: Economic Aspects
Thanks this helps a lot!