Comment #4 on issue 2930 by [email protected]: Patch: Allow \tag to accept multiple tags, like \keepWithTag and \removeWithTag do.
http://code.google.com/p/lilypond/issues/detail?id=2930
Regarding comment #2: I can't think of a situation where this would make sense. Their tags mark specific points/labels for insertion rather than being part of a general include/exclude mechanism.
