In the '30s, Billie Holiday's singles showed what vocalists could bring to jazz improvisation. On her early takes of songs like “These Foolish Things,” her tightly controlled vibrato created drama with ease; her bluesy, teasing use of sustained notes set up a rush of swinging syllables, showing off her wit and sensuality. During later sessions for the Commodore and Verve imprints, Lady Day used fresh phrasings when singing familiar songs like “Good Morning, Heartache,” which were often given new symphonic arrangements. No matter the style of the session, her singing was always elegant and original.