Which tag should be used for a concert hall ?

besides the first comment, you can also use amenity=theatre (which is often used for operas et al), if it is concentrating on "classical music" - Info here: http://wiki.openstreetmap.org/wiki/Tag:amenity%3Dtheatre

Smaller concert halls (which host e.g. aves, rock concerts) can also be tagged with amenity=nightclub: http://wiki.openstreetmap.org/wiki/Tag:amenity%3Dnightclub

If it is a multi-purpose hall (where not only/mainly concerts are held), you can also use amenity=community_centre - info here: http://wiki.openstreetmap.org/wiki/Tag:amenity%3Dcommunity_centre

The borders between pub/restaurant/cafe/disco/nightclub and also theatre/opera/multi-purpose-event-hall is also irl very blurry, so use your common sense ;)

This subject has recently (July 2015) come up again on the talk mailing list. A wide range of tags are in use:

• Albert Hall, London: attraction=music_venue
• Concertgebouw, Amsterdam: amenity=theatre
• Gewandhaus, Leipzig: theatre:genre=philharmonic
• Musikverein, Vienna: amenity=concert_hall
• Philharmonie, Berlin: amenity=theatre
• Symphony Hall, Birmingham: building=concert_hall

Clearly the only appropriate tag is amenity=concert_hall. These are not theatres.

I suspect that amenity=theatre is widely used because these are relatively important destinations in large cities and theatres are rendered. This is therefore a case of "Tagging for the Renderer". If contributors feel that losing the rendering is too much of a deficiency I would suggest adding theatre=concert_hall as an interim measure.

I am submitting an issue for the CartoCSS style to render amenity=concert_hall to discourage this widespread practice.

Equally, abusing amenity=nightclub, neither helps locate music venues or helps those searching for the social life associated with nightclubs. Places such as Rock City in Nottingham are primarily music venues, but at present I do not find a good tag for these.