In its early years, its title included the addition "(with or without a conductor)".
According to the Academy, "the Chamber category was folded into the Small Ensemble category, the only distinction having been the number of players in the group (Chamber being smaller), and the fact that Small Ensemble recording could, though not necessarily, employ a conductor."
[1] In the new structure, recordings are eligible if the ensemble contains 24 or fewer members, not including the conductor.
In 2013, the category was renamed as Best Chamber Music/Small Ensemble Performance.
The producer(s) and engineer(s) also receive an award if they have worked on over 50% of playing time on the album.