Great singers are often gifted mimics.
The ability to imitate what you hear, especially if it’s done well enough to win over an audience, is a skill that has direct impact on your performance level. If you can imitate whatever you hear, you can perform anything. And if your ear is keen enough to catch the details of another person’s sound well enough to mimic it, it is keen enough to do just about anything.
Two examples leap to mind.
First, Ella Fitzgerald: perhaps one of the most gifted singing mimics ever. Her legendary “Mack The Knife” from Ella in Berlin is the most famous, but I’m thinking of her version of “Bill Bailey, Won’t You Please Come Home” from Twelve Nights in Hollywood. The range of singers she imitates is remarkable (including, between the song and the reprise, Louis Armstrong, Jimmy Durante, Sophie Tucker, Della Reese, Dinah Washington, and Pearl Bailey!).
Second, the godfather of vocalese, Jon Hendricks. He, of course, is best known for his lyrical imitations – writing and performing lyrics to instrumental jazz solos that call to mind the original solos in tone, phrasing, and lyrical idea. But he also had this remarkable turn with his vocal trio, Lambert, Hendricks, and Ross, imitating various jazz bassists: Percy Heath, Paul Chambers, Ray Brown, and Charles Mingus.