Factual error: When the band are playing "March of the Cobblers" at Saddleworth, Andy (tenor horn) and Harry (euphonium) are heard playing the main tune of the march. In real life however, these two instruments do not play the tune, they have separate parts for the accompaniment.
Visible crew/equipment: When Jim gives his donation to Danny just after Gloria walks into the practice room for the first time, a microphone can be seen reflected in his tuba bell.