Stupid iTunes question

So iTunes thinks I have a lot of "duplicate music". That's because iTunes is stupid, and doesn't realize that a live album will have a different version of a song; the four-minute difference in length is a good indication of that.

But some of the music really is duplicated. For instance, I have "We Walk" by R.E.M. on their album "Murmur", and also on "Mary Had a Little Amp". It seems to me that I don't really need to keep two files around when I could keep one. But! If I delete, say, the one from "Murmur", then when I tell iTunes, "Play me everything from Murmur", it'll miss a song.

Is there any way to convince iTunes to file a song twice based on a single file?