Annabella Lwin. Although her real name is Myant Myant Aye (she’s originally Burmese).
Rich was 16 and Chris was 18 when they formed the Black Crowes in 1985. But Shake Your Money Maker, their first album, didn’t come out until 1990 when they were both past 20.
Mike Oldfield was still in his teens when he recorded most of Tubular Bells, and was still a few months short of 20 when it was released.
It was an amazingly inventive contribution to rock music. No lyrics! A continuous instrumental work without track breaks! The use of over-dubbing to allow one intrumentalist to become a ‘one man orchestra’! The mix of rock, folk and other textures into what would later, much later, became the genre known as ‘New Age’.
A number 1 album in countless territories. Has sold over 16 million copies around the world. Spawned any number of imitators and also helped to give the world the Virgin business empire (good thing or bad, discuss).
Quite an achievement.
Menudo. Though I wonder how much an accomplishment it is when the “band” is formed by the producers and being a teenager almost means you’re too old to still be in it.
I may be wrong but wasn’t Todd Rundgren still a teenager when he was in the Nazz?
U2 formed when Larry Mullen, then aged 14, posted a notice at his high school looking for people to be in a band. Bono (well, just plain old Paul Hewson at that point) and Adam Clayton, the two oldest members of the band, would have been 16 and The Edge (again, just Dave Evans then) would have been 15 at the time the band formed. Bono wrote the lyrics for the song “Out of Control” on his 18th birthday, and while Bono and Adam Clayton were 20 by the time their debut album Boy was released, The Edge and Larry Mullen were still teenagers.
I saw a kid play with Gregg Allman - his name was Derek Trucks, IIRC. He was maybe 14 or so, and an incredible guitar player.
The Runaways, (Joan Jett, Lita Ford, et al), were all teenagers when they broke.
Eddie Cochrane, (‘Summertime Blues’), and Ritchie Valens, (‘La Bamba’), were teens.
The drummer on the first Santana album, (Santana), Michael Shreive, was 16.
About Winwood; I’d always heard that ‘Gimme some lovin’ was recorded when he was 17, and that ‘I’m a Man’ was recorded when he was 18. (Regardless, his voice kicks butt).
The Small Faces were still teenagers when they had their first hit, ‘Wotcha gonna do about it’ in 1965.
well, just, wow.
The Australian band Silverchair broke big when the members were all between 14 and 16 (depending on the source). They’re a bona fide rock band, writing their songs, playing their instruments, making it on their own, etc.
Björk was eleven when her self-titled album was released. It wasn’t exactly hard rockin’ but it had a Beatles cover (Nowhere man) on it, so I guess it counts.
She was sixteen when she fronted Tappi Tíkarrass (“Cork the Bitch’s Ass.”) A little edgier than her earlier effort.
Remarkably, her voice has hardly changed at all from the way it was in that first recording.
I was told that Chris DeGarmo of Queensryche was 17 when the band recorded their self-titled debut EP.
Nils Lofgren was 17 when he did the piano part on Neil Young’s “Southern Man.” The story (from Shakey by Jimmy McDonough) is that Neil decided to test Nils by telling him he was going to play piano on a song the next day. Nils said, “I’ve never played piano in my life.” Neil said, “Yeah, I know–but I want you to play piano.” So Nils kept trying to come up with something and was just pounding on the keyboard when Neil said, “That’s the solo.”
Correction: DeGarmo formed Queensryche in 1981, when he was 17; their debut EP was released in 1981, when he was 19.
[sub]Note to self: check facts first, post second[/sub]
Two excellent young guitarists:
Jonny Lang was only 15 years old when his first solo album Lie to Me (#44 on the Billboard chart, #1 on the blues chart) was released. He was the leader of the “Bad Medicine Band” when he was 12, and by the time he was 15 he had already released 3 albums!
Kenny Wayne Shepherd released Ledbetter Heights (#108 on the Billboard chart, #1 on the Blues chart) when he was 18.
You can start at the very beginning of it, with Elvis, Richie Valens, Etta James, on and on. Unless you wanna say Elvis ain’t Rock ‘n’ Roll, in which case we have nothing further to discuss. 
More recently, how old were the guys in Modest Mouse when they started out?
Even more recently, Smoosh started out as pre-teens. (It’s not great music, but it’s fun. And how many people can boast that they’ve opened for Pearl Jam before hitting puberty?)
Helen Shapiro had a UK number 1 with “Walking Back To Happiness” in 1961 when she was just 14.
The Beach Boys spanned the ages of 14 - 18 when they got started. It’s safe to say they made a mark.