Welcome aboard, NHJohn!
While I'm not sure about the Old Capitol Prison, I do know that according to a newspaper article we found back in 2012 that 10 drummer boys played a "somber cadence" at the execution of the Lincoln Conspirators at the Old Arsenal on July 7, 1865.
Here is the post describing this article as well as an MP3 of a military cadence we found entitled "Execution Cadence." It was supposedly one of the easiest pieces to play and while a complete band wasn't used at the execution as far as we know, this may be the last "music" heard by the hapless foursome, Surratt, Powell, Herold and Atzerodt.
http://rogerjnorton.com/LincolnDiscussio...ht=Drummer
