This is from actual Army b-roll archives.
On October 21st, there were two Marines from the 1st Marine Expeditionary Force, just inside Fallujah, singing...well...just hit the link and watch/listen (or you can "right click" -> "save as" to download. It's 7.75 MB).
I don't think that I've heard a more beautiful sound. If this isn't worksafe for you, then you must work in France.
The Marines are Corporal Mark Sixbey (from Metlakatla, AK) and Sergeant Robert Jones Jr. (from Oceanside, CA).