Watch a 14-Year-Old Amy Winehouse Sing 'Happy Birthday' Like No Other in New Documentary 'Amy'

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She could belt one out even at a young age.

Amy Winehouse certainly was capable of commanding a room -- even at a young age.

In the upcoming documentary Amy, the poignant opening scene shows the late singer, at only 14, making the all-too-familiar "Happy Birthday" song all her own at a party for her friend, Lauren Gilbert.

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Not surprising, the sound of her powerful voice leaves everyone speechless.

"There are a group of friends that she's with that are really close to her, they're sisters essentially," Amy director Asif Kapadia told ETonline about the unforgettable scene. "It's three girls, Amy is one of them, Juliette [Ashby] and Lauren are the other two, and they just grow up together and there are, unfortunately, the way things transpire, they get separated. But the film begins with the three of them just messing around at a birthday party and they're just kids and you kind of think, 'What a weird way to open a film.'"

Weird? Perhaps. But the moment nevertheless serves as a perfect introduction -- as well as a reminder -- of Winehouse's enormous skills as an artist, one who was taken from us way too soon. The "Rehab" singer was only 27 when she died in 2011 from alcohol poisoning after a long battle with substance abuse.

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"You hear the voice, you can see her, she’s playing Marilyn Monroe, she's doing all these things with a lollipop stick as if it’s a cigarette and she just plays this character and you can see it," Kapadia added. "It was all there. It was perfectly formed at the age of 14. She had it all already. It's only two years later she was then performing, it's only three years later she’s having these really intense relationships and making songs out of them, with older men. So you can see already she was a mature girl at 14. So that opening scene I think makes a lot of people go 'Wow.'"

The documentary shows even more never-before-seen home movies of the star and focuses on her obvious love for music -- revealing a happy, energetic young woman with a wicked sense of humor. There are also several laugh-out-loud moments, including her unapologetic interviews during the first press tour for the album Frank.

Of course, the film becomes quite heartbreaking at times as it delves into Winehouse's eventual spiral into drug addiction.

Watch the haunting full trailer for Amy in the video below. The film hits theaters on July 3.

Sophie Schillaci contributed to this report.