All very true, Julia. I would only add that real classical music (say, Rossini's "William Tell Overture," composed in 1829, or opera) could be heard mainly in concert halls in a few big cities like Boston, New York, and Philadelphia. But well-to-do "Civil War people" certainly were familiar with it.

Since this is a "folk music" forum, let me add something about folk music. It's a popular practice to day to sing traditional songs to a lone fiddle accompaniment, but to judge from the comments of later folksong collectors, that practice was extremely rare. "Spanish guitars" were not very common nationally, autoharps uninvented, dulcimers known mainly in the Appalachians, hammered dulcimers rare and expensive.

Even among Irish immigrants, uillean pipes were extremely rare (very expensive). Some Scots immigrants played bagpipes, but they were still solo instruments and not used in marching bands as they were in the British Army. Flutes, of course, were easily portable.

Minstrel troupes typically used a fiddle, a banjo, a tambourine, and a pair of bones. Outside of the drums and wind instruments of military bands, these, plus the recently invented harmonica, were the typical instruments one might find in an army camp on either side. I can't recall any reference to tin whistles, but they were cheap and available.

The most typical musical sound of the period, other than that of the fiddle, flute, banjo, parlor piano, minstrel performance, or fife and drum corps may have been that of the brass band, military or civilian, which played all sorts of music.