I can't think of any place i've seen it, or explain how it goes, but there is a song that is played to footage of the Vietnam war. I have always associated this song with smoking weed, and I am sure that's what it really is. All I know is that usually the footage of the war is showed from a camera moving to the right.
Im not sure I know what Vietnam footage you are speaking of, but I do know that you can hear these songs on alot of vietnam movies: Run Through the Jungle by Creedence Clearwater Revival; Turn, Turn, Turn by The Byrds; In the Year 2525 by Zager and Evans; Light my Fire and Break on Through to the other Side by the Doors.
Check these out, see if that is what you are looking for.