BAM is about more than music -- it is a performing arts mecca. Film, theater, dance AND music all have homes here (and if you can ever rehearse in their spaces you will feel like you have died and gone to theatrical heaven).
This is one spot in Brooklyn that is definitely worth the trip for any Manhattanite -- not only do they bring in great tours of shows, but have a stellar lineup from local artists as well. The subway is not that far away and they also offer bus services from the city before showtimes (check the BAM website for more detailed information).
The building itself is beautiful.