Azizi, thank you for this post. Very informative. My observation of jazz singers is that the Black singers tend (Ella, Sassy, Billie etc.) to use a balanced voice rather than an obligatory belt which is often the product of White singers. I think this may be the effect of the African-American Church as it often acts as a cultural basis for Black jazz singers. The result is that there is a deeper presence in the voice through modulated singing rather than the thinning out of the voice through too much belting.

This is not a racial observation but a cultural one. There is however a propensity for the African-American singing voice to have a strength and flexibility that is suited to this singing style. Again, this is a tendency, not necessarily true in all cases.

There physiology and culture intersect is in the approach to this singing style using a balanced voice with ornamentation that carries over into jazz.

Frank