As for her voice: where does it come from, this extraordinary sound?
The music poures out of her, a stream of weathered, seasoned phrases, seemingly without effort, and mercifully without any of the ululating and over-emoting that blights so many performances in the soul-jazz field in which Winehouse operates.
For her, what matters is the quality of the notes, not the quantity.
Amy Winehouse is, of course, almost as famous for her behaviour as for her music; tabloid newspapers in recent months have been peppered with the striking visage of this north London Jewish girl, accompanying lurid reports of her latest night on the razz. But here, on this fantastic set, she'd done so in moderation, because she seemed focused and together.
"Back to Black", is a more soulful and stripped-down collection than her jazzier debut, "Frank". The influence of girl groups from the 1950s and early '60s is plain: plinky keyboards, parpy brass, trebly guitar.
Some excellent background vocals provides weight and depth, while she and her band do a brilliant job of recreating the big soulful sound conjured up in the studio by producer Mark Ronson.
In songs such as "Me & Mr Jones", "Back to Black", "Love is a Losing Game" and "Rehab", we may hear the sound of Phil Spector, of Muscle Shoals, of the Shirelles and the Supremes.
But this is no mere retro soul show: these are not pastiches, but real emotional journeys from a woman with real emotional experiences.
She is a standout talent with a nice line in bitchy put-downs and a wondrous voice reminiscent of Dinah Washington.
Even so, her second album has surpassed all expectations.
This is the best British soul album in absolutely ages, a complete package of lovingly recreated Motown/60s girl group sounds, caustic, often excruciatingly honest lyrics, great finger popping tunes and a voice that does sexy and smouldering and dismissive contempt with equal alacrity.