Recital Hall acoustic help needed

I own a recording studio, so this site and homerecording.com are well known to me, but my piano tuner asked me for help with treating a room he wants to turn into a recital hall. Anyone willing to help out here? If so, I'll point him in this direction.

I only know that it is an entirely different set of considerations. What would be considered a good recording or control room would be considered WAY too dead for a recital hall.

How large a room are we talking about here, and roughly how many bodies will be listening typically? This all needs to be considered for concert/recital acoustics; in larger rooms, even the air needs to be factored into absorption curves... Steve