Click to listen to Britney Spears' "Till the World Ends"

Britney Spears is pop music's stealth avant-gardist. For years, critics have dismissed her as a cipher with a wisp of a voice. But from the minute she burst on the scene — heralded by the keyboard power chords of ". . . Baby One More Time" — her music has steered bubblegum into weirder, woollier territory. "Toxic" was a mélange of Bollywood and spy-movie guitar; "Piece of Me" was an essay on 21st-century tabloid infamy crooned over 22nd-century club rhythms. Then there's this year's "Hold It Against Me," which dissolves into a furious dubstep breakdown — easily the most assaultive beat on the Hot 100 right now.

Click to listen to Britney Spears' "Hold It Against Me"

Femme Fatale may be Britney's best album; certainly it's her strangest. Conceptually it's straightforward: a party record packed with sex and sadness. Max Martin and Dr. Luke, the world's two biggest hitmakers, are responsible for seven of 12 songs: big melodies and bigger Eurodisco thumps. But other producers go nuts, tossing the kitchen sink at Britney. The Bloodshy-helmed "How I Roll" is sputtering, oddly beautiful techno. In "Big Fat Bass," Will.i.am turns Britney into a cyborg obsessed with low-end. ("The bass is getting bigger!" she exults.) On nearly every track, Britney's voice is twisted, shredded, processed, roboticized. Maybe this is because she doesn't have much of a voice; it's certainly because she, more than almost any other pop diva, is simply game. Femme fatale? Not so much. But say this for Britney: She's an adventuress.

Britney Spears: A Life in Photos

“All Along the Watchtower”

Jimi Hendrix got hold of Bob Dylan's early John Wesley Harding tapes and in late 1967 recorded a version of "All Along the Watchtower" with the Experience in London. Dissatisfied with that first development, Hendrix brought those tapes with him to New York in early 1968 when he began work on Electric Ladyland. Eddie Kramer, Hendrix's engineer at the time, told Rolling Stone that Hendrix "was still looked upon by his basically white audience as the mammoth black guitar hero. There was a constant fight within him to expand himself." Hendrix's successful take on Dylan's work has long been recognized by the songwriter. "I liked Jimi Hendrix's record of this and ever since he died I've been doing it that way," Dylan wrote in the liner notes to his Biograph box set. "Strange how when I sing it, I always feel it's a tribute to him in some kind of way."