Don't recall us touching on this subject but they sure are vital, whether long-term or put together for a tour (I make and Wiki makes a distinction between session folks who generally don't travel and back-ups who do) Also they have to have a name, not just The [Artist] Band. I'm drawing from this Wiki:

Ace in the Hole:
Scarlet Fever: << All-female band
The Hot Band: << May be the best ever BU band
Flecktones: << a 2-hour concert so you can fully savor the flavor
The Aces: << Full concert at the Beeb

Let's have some fun with this--cut in your faves.