May I present three very interesting ladies from The Jazz Age:
Helen Morgan, Ruth Etting and Libby Holman.
In addition to the same hair and make-up style, Helen, Ruth and Libby all worked in films and on stages in the 1920's and 1930's. They were actresses and furthermore so called torch singers, singing torch songs. Male singers were called crooners.
Torch songs were sad songs about heartbreak and failed romance so of course you need to sing in a very delicate way. Luckily, since the introduction of electric microphone in 1925, it was possible to sing in a more intimate and hushed style instead of vaudeville robust belting.
The microphone opened a new way of singing. A quality microphone will capture each little tone. For a singer this is both an advantage (when you feel like really diving into intonation and interpretation) yet also risky business (when you haven't slept well and feel a flu coming).
However, new to the new microphone techniques, Helen, Ruth and Libby hadn't quite figured out how to use this world-changing technology. When singing into a mic they still counted on the old habits: repeated wailings, emotional gurglings and chin quiverings.
Sounds quite interesting actually. I might try it myself.