No, not the high pitched 'hallelujahs' kind of choir. A Choir, in angelic terms, is a rank or group of angels. These groups perform different functions in the Universe.
Archangels are the most frequent angels mentioned. They are messengers between Deity and humans in times most needed.
All the choirs serve different functions and some angels have multiple ranks, along with multiple functions. Angels aren't limited to angels when working either. They have been known to work with faery, dragons, and other spirits.