I think many people have experienced this situation already:
You play a nice WAD but find the music choice of the creator dreadfully awful and want to change it to something from your music library collection.
As long as it's only using MAPINFO to define music this is not really a problem and can be changed quickly.
However, an increasingly large number of maps is changing music from within ACS and no simple approach to replace this music exists aside from replacing the actual music lumps in the WAD itself.
So how about a $musicalias command with which you can remap specific music titles to others? Optionally an ignore command could be nice which would disable switching to specified musics at all.