The Lester S. Levey Collection held by the library at Johns Hopkins University is wonderful---the Civil War era sheet music is all DOWNLOADABLE. Here's a blue clicky to send you to the university's library. www.jhu.edu/library
Once you hit that web site, chose the library Special Collections list. Then click on the Lester S. Levey Collection.
    Speaking of Civil War music, has anyone else commented on the similarities and differences between Stephen Foster's "Gentle, My Darling" a popular hit of 1861, the summer the War started, and "Who Will Tell his Mother, that her Poor Boy is Gone," a song sung in 1862 at the time of the Battle of Antietam (26,000 men killed, wounded or missing in action in one awful day).
    If you ever get to Sharpsburg (near the Antietam Battlefield) ask for a tour of the Christ Reform Church on Main Street. It was a field hospital for Confederates and Union soldiers after Antietam. The stained glass windows tell a war story.