Here is a website I just found with credits for the shows playing on Broadway: http://www.ibdb.com/default.asp Frank Greene on trumpet and former Mouseketeer Cubby O'Brien on drums in The Producers!
How often is that updated? I saw "Movin' Out" last week on Broadway, and Carl Fischer was playing trumpet, not Barry Danielian.
They are listing opening night personnel, if they list them at all. This is a good historical source. Wilmer