I've seen it in original network airing and I remember it being silent. I'm saying I'm 99% (but not 100%) sure that it's silent. The sequence's use of silence sticks out in my mind for being, well, silent.
Wasn't the Wagner tune used when they 'avenge' the Old Man's murder in Roosters?
As you say, why wouldn't they use free music when they spent the money to license other songs? Plus, I'm sure someone would have caught that by now since S2 is the most beloved Millennium season ever.