Some Jazz bands operate under a kind of aesthetic mandate, imposed by a bandleader in search of a sound. Many are much looser, allowing for whatever happens in the combination of certain ingredients. The drummer Billy Hart, who has had a busy career in New York and abroad since the late 1960's, trusts his musicians and encourages them t expand their ideas as they see fit. Here is a band of musicians who let their imaginations take them down their respective roads and yet merge together for a unified sound that transcends the individual players.