Depends on the voice. Trombone is in the tenor range. Flute and violin soprano. Viola and upper cello..alto. Baritone....baritone horn. Bass, small tuba or bowed bass. As to the frequency range by which the "timbre" of the instrument is measured, every voice is slightly different. The flute can sound like some sopranos...breathy and high-pitched without jarring frequencies. The sax can be played smooth like Paul Desmond or Lee Konitz and more cutting like Charlie Parker. These instruments really are the "voice" of the players.
The difference in vocal quality is more contrasting then these other instruments mentioned.
Louis Armstrong vrs. Jussi Bjorling for example. Apples and oranges.
I find many human voices irritating to listen to if they don't have the musical phrasing and sophistication of a Louis Armstrong or Renee Fleming. I like the shouters if they are the real deal like Big Bill Broonzy.
I may be one of the few folkies that likes Ethel Merman..the belt queen. You woulda' had to seen her to believe it.
i would rather hear the cutting edge of a Bird solo than the baleful whining of some of the new folkie-types with their breathy and innocuous made-up ballads.
The African-American voices are beautiful and sound trumpet-like and some like a sax.
The sax is fundamentally a jazz instrument, Sigfried Rasher aside. (Classical sax player..think I have his name right if not please correct)
Some love the wide vibrato of Sidney Bechet, others hate it. I have heard African-American voices that sound this way.
Louis when he sings growls like Kid Ory's trombone.
Some baritones with rich voices in the folk field such as Stan Rogers remind me of baritone horns or low french horns.
Billie Holiday reminds me of a soft clarinet...with a bit of a growl.
I love the sound of the Celtic Women and Mairead Nesbitt makes her violin sing like a great soprano voice.
Almeda Riddle and Texas Gladden remind me of the sound of an folkie oboe. The appalachian trad male singers (Horton Barker) like an English horn. This would be true also of Bulgarian Women's choruses.
Judy Collins sounds like a smooth viola.
The human voice may be the most versatile instrument of all because of its variety of tonal quality. It can sound like many instruments.