It was one of those little rituals that speaks volumes about the nature of music in New Orleans, and New Orleans musicians.

When the car containing Willie Humphrey would pull up in front of Preservation Hall to deliver the clarinetist to his usual Saturday night gig, a middle-aged street musician who often entertains the people waiting in line outside the club would respectfully silence his saxophone, then introduce Humphrey.

"Do you know who this is?" the street musician would announce...