Comment on Sarah. She is missing from my 'studies', and I'm so surprised to hear her version of "Motherless Child". What I have always heard from her, and passed over from her, frankly, was much harsher and lower in timbre. Further analysis of Vaughan from Wiki:
Voice
Parallels have been drawn between Vaughan's voice and that of opera singers. Jazz singer Betty Carter said that with training Vaughan could have "...gone as far as Leontyne Price." Bob James, Vaughan's musical director in the 1960s said that "...the instrument was there. But the knowledge, the legitimacy of that whole world were not for her...But if the aria were in Sarah's range she could bring something to it that a classically trained singer could not."
In a chapter devoted to Vaughan in his book Visions of Jazz (2000), critic Gary Giddins described Vaughan as the "...ageless voice of modern jazz – of giddy postwar virtuosity, biting wit and fearless caprice". He concluded by saying that "No matter how closely we dissect the particulars of her talent...we must inevitably end up contemplating in silent awe the most phenomenal of her attributes, the one she was handed at birth, the voice that happens once in a lifetime, perhaps once in several lifetimes."
Her voice had wings: luscious and tensile, disciplined and nuanced, it was as thick as cognac, yet soared off the beaten path like an instrumental solo...that her voice was a four-octave muscle of infinite flexibility made her disarming shtick all the more ironic" – Gary Giddins
Vaughan's New York Times obituary described her as a "singer who brought an operatic splendour to her performances of popular standards and jazz." Fellow jazz singer Mel Tormé said that Vaughan had "...the single best vocal instrument of any singer working in the popular field." Her ability was envied by Frank Sinatra who said that "Sassy is so good now that when I listen to her I want to cut my wrists with a dull razor." The New York Times critic John S. Wilson said in 1957 that Vaughan possessed "what may well be the finest voice ever applied to jazz." Age hardly affected Vaughan's voice. Her voice was still close to its peak before her death at the age of 66. Late in life Vaughan retained a "youthful suppleness and remarkably luscious timbre", she was also still capable of the projection of coloratura passages described as "delicate and ringingly high".
Vaughan had a large vocal range of soprano through a female baritone, exceptional body, volume, a variety of vocal textures, and superb and highly personal vocal control. Her ear and sense of pitch were just about perfect, and there were no difficult intervals.
In her later years her voice was described as a "burnished contralto" and as her voice deepened with age her lower register was described as having "shades from a gruff baritone into a rich, juicy contralto". Her use of her contralto register was likened to "dipping into a deep, mysterious well to scoop up a trove of buried riches." Musicologist Henry Pleasants noted that "Vaughan who sings easily down to a contralto low D, ascends to a pure and accurate [soprano] high C."
Vaughan's vibrato was described as "an ornament of uniquely flexible size, shape and duration,"[18] a vibrato also described as "voluptuous" and "heavy" Vaughan was also accomplished in her ability to "fray" or "bend" notes at the extremities of her vocal range. It was noted in a 1972 performance of Leslie Bricusse and Lionel Bart's "Where Is Love?" that "In mid-tune she began twisting the song, swinging from the incredible cello tones of her bottom register, skyrocketing to the wispy pianissimos of her top."
Vaughan would use a handheld microphone in live performance, using its placement as part of her performance. Her various placings of the microphone would allow her to complement her volume and vocal texture, often holding the microphone at arms length and moving it to alter her volume.
Vaughan would frequently use the song "Send in the Clowns" to demonstrate her vocal abilities in live performance, it was described as a "three-octave tour de force of semi-improvisational pyrotechnics in which the jazz, pop and operatic sides of her musical personality came together and found complete expression" by the New York Times.[16]
Singers directly influenced by Vaughan have included Phoebe Snow, Anita Baker, Sade and Rickie Lee Jones.[16] Singers Carmen McRae and Dianne Reeves both recorded tribute albums to Vaughan following her death; Sarah: Dedicated to You (1991) and The Calling: Celebrating Sarah Vaughan (2001) respectively.
Though usually considered a "jazz singer", Vaughan avoided classifying herself as one. Vaughan discussed the term in an 1982 interview for Down Beat:
"I don't know why people call me a jazz singer, though I guess people associate me with jazz because I was raised in it, from way back. I'm not putting jazz down, but I'm not a jazz singer...I've recorded all kinds of music, but (to them) I'm either a jazz singer or a blues singer. I can't sing a blues – just a right-out blues – but I can put the blues in whatever I sing. I might sing 'Send In the Clowns' and I might stick a little bluesy part in it, or any song. What I want to do, music-wise, is all kinds of music that I like, and I like all kinds of music."