On principal, I always endorse live music over canned, if for no better reason than to support and encourage musicians.
It's a bad PR look, though, because it demonstrates that you can't fill your stadium, and you
knew long before the game that you couldn't fill your stadium.
It
could be effective as advertising, on a temporary basis, if the sound of the band attracted students who were on campus to come check out the scene (depending on student admission prices).
As for live music that would enhance the event or the fans experience...
1) If fans totally love hearing that band in other venues (football or basketball) so there's already an energy connection by association, maybe it could work.
2) But baseball is so different from other sports spectator experiences, so if I was going that route, I'd look for a totally different combination of instruments and music... maybe a jazz-savvy quintet with a broad repertoire.
3) Baseball's pace allows for /calls for the music to have wit and situational awareness, which means a broad repertoire of memorized songs.
4) Can they provide each player's walk-up music? Mixing canned and live music almost always leaves one or the other sounding worse than either alone.
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Yeah, I gotta say no.
UNLESS... [see follow-up post]