All of the sudden I remembered a story - whether it's from actual history or a book I read a while ago, I don't remember - where one army ambushed another with music from their homeland, greatly inhibiting their will to fight. Or something along those lines. It might have been in Asia and in a mountain pass. Anywho, what do y'all know about this topic?
Also, not sorry about my usage of "instrumental."
You're thinking of the Battle of Gaixia, the end of the Chu-Han civil(?) war. The Han forces surrounded the Chu, and played Chu music to remind the weary soldiers of their families. The Chinese idiom 四面楚歌 (literally, "Chu music on all sides") is now used to indicate being stuck in a terrible situation.
Our source for this is Records of the Grand Historian (史記) by Sima Qian (司馬遷). It is the "official" history of China up until that point, so to speak. How reliable a single source can be is of course, up for debate. I am unfamiliar with the historian's opinions of this work, but it has been treated as reliable by centuries of Chinese scholars.
My favourite story is from the Fetterman Massacre which includes a story about the bugle-player using his instrument as a weapon as a last ditch attempt to fight the Native Americans. All of the United States soldiers' bodies were mutilated except for his - as he was praised by them for his bravery.
Well, it wasn't a success, but it was instrumental ;)