By the way, if the creator of copyrighted stuff is already dead, it doesn't mean nobody has the copyright any more. His closest relatives inherit that copyright. Which lasts for 70 years after the day the creator dies.
That's true, in addition to that: If there is no creator (no PERSON, just a organisation like a radio station or such things) the copyright lastes 70 years after the day it has been recorded.
So the most music from the late 30s is still under copyright.
But there is a way: Most of the famous marches are from the late 19th century.
So, find a man with a synthesizer an give them a sheet of music.
I knowed someone at the the dmp board, but he had left a long time ago.
(he was a guy from Uk. a professonal musician, don't remeber his name.... )
maybe you can find help here:
german gamedev board
or here
THE gamedev board - international
i can ask around if you want(need) my help.