What role did the clarinet play in a New Orleans jazz ensemble?

In a New Orleans jazz ensemble, the clarinet played a vital role within the polyphonic collective. Specifically, it was responsible for performing obbligato or descant functions in a high register, providing a melodic layer that complemented the other instruments.1

While the cornet typically stated and embellished the main tune in the middle range, the clarinet’s high-register lines were part of the ensemble's "brilliant solution" of emphasizing independent but harmonically linked, simultaneous melodies. In this format, the clarinet, along with the trombone, often played these obbligato parts while other instruments occupied the foreground or provided a harmonic foundation. As the style evolved, musicians began to improvise fresh melodies and obbligatos of their own making, though these remained within the framework of the tightly integrated collective ensemble.12