Holiday is often considered the foremost female singer in jazz history, a view substantiated by her influence on later singers. Her important work is found in the group recordings made mostly for Hammond between 1936 and 1944. Her vehicles were mainly popular love songs, some of them long forgotten, others among the best of the time. Her voice was light and untrained, but she had a fine natural ear to compensate for her lack of musical education. She always acknowledged her debt to Armstrong for her singing style, and it is certainly in emulation of him that she detached her melody line from the ground beat, stretching or condensing the figures of the melody, as on the opening of Did I Remember? (1936).

More than nearly any other singer, Holiday phrased her performances in the manner of a jazz instrumental soloist, and accordingly she has to be seen as a complete jazz musician and not merely a singer. Nevertheless, her voice, even in the light and lively numbers she often sang during her early period, carried a wounded poignancy that was part of her attraction for general audiences. Although Holiday claimed also to have taken Bessie Smith as her model, she sang few blues, and none in the powerful, weighted manner of Smith. She was, however, a master of blues singing, as for example on Fine and Mellow (1939), which she built around blue thirds descending to seconds to create an endless tension perfectly suited to the forlorn text.