Full-length albums still serve a purpose as artistic and marketing focal points. But as soon as they come out, we take them apart and put them back together in personalized playlists. Here's my lucky 21 for '09, designed to fit on a CD, with no overlaps with my Top 10 album lists. And there's a streaming playlist on my blog, at www.philly.com/philly/blogs/inthemix.

1. "Boom Boom Pow," Black Eyed Peas. Onomatopoeic, irresistible, and ubiquitous hit from will.i.am, Fergie, and those two other hip-pop Peas whose names nobody knows.

2. "Bad Romance," Lady Gaga. She wants your disease. And what Gaga wants, Gaga gets. Deservedly so: The fashion-forward, glam-dance neo-Madonna rewards much closer attention than the original these days.

3. "She Wolf," Shakira. Slithering disco that rhymes "A domesticated girl, that's all you ask of me," with "Darling, it is no joke, this is lycanthropy." Ridiculous, and ridiculously entertaining.

4. "Bulletproof," La Roux. British electro duo of swooshy-haired front woman Elly Jackson and synth-man Ben Langmaid come on like the Pet Shop Boys on Red Bull. That's a good thing.

5. "Stillness Is the Move," Dirty Projectors. This Brooklyn band mashes up African, R&B, and indie influences. I'm sticking with the original sung by Amber Coffman, though Solange Knowles' cover is pretty awesome, too.

6. "Warm Heart of Africa," The Very Best featuring Ezra Koenig. Koenig, the Vampire Weekend singer, meets an Afro-Euro band on a song named after a Malawi tourist slogan. Ebullient internationalist pastiche of the year.

7. "New in Town," Little Boots. Brit electro-pop starlet Victoria Hesketh looks for a good time, despite being broke. Sounds like 2009 to me.

8. "Two Weeks," Grizzly Bear. Sublime chamber-folk choral precision from Brooklyn indie darlings.

9. "Pro Nails," Kid Sister featuring Kanye West. Chicago rapper's long-awaited Ultraviolet disappointed, but this twitchy trip to the nail salon was worthy of the buzz.

10. "Can't Stop Partying," Weezer featuring Lil Wayne. The vegetarian ascetic Rivers Cuomo ironically promises to debauch himself, with Lil Wayne pouring the Patron.

11. "Party in the U.S.A.," Miley Cyrus. Autobiographical bubblegum details the teen trauma of going Hollywood.

12. "American Saturday Night," Brad Paisley. Country guitar man's tasty melting-pot celebration of French kisses, Spanish moss, and Italian ice.

13. "Love Story," Taylor Swift. She won the Kanye brouhaha, and everything else. This down-to-earth fairy tale showcases the crafty songwriting that's packaged with the curly locks of the leggy Ms. Swift, who turns 20 today.

14. "Summertime Clothes," Animal Collective. Showered with praise upon the release of its album in January, the Baltimore-Brooklyn indie trio's Merriweather Post Pavilion gets murky over the long haul. But this seasonal confection catches you up in its psych-pop swirl.

15. "A Strange Arrangement," Mayer Hawthorne. DJ Andrew Cohen takes his middle name and the street he grew up on as an alias, and becomes a suavely confident Curtis Mayfield-style soul man.

16. "The Sweetest Thing," Camera Obscura. Delectable indie pop off My Maudlin Career, from the Glaswegian band fronted by Tracyanne Campbell.

17. "People Got a Lot of Nerve," Neko Case. Art-country siren proclaims herself a "maneater" of willing prey.

18. "Kick Drum Heart," Avett Brothers. The North Carolina roots band kicks it up-tempo on a highlight from its major-label debut.

19. "Kiss With a Fist," Florence and the Machine. Rising Brit Florence Welch, who conjures Kate Bush, shows her punky side with a jab to the kisser.

20. "Golden Phone," Micachu. Classically trained British wunderkind Mica Levi makes experimental art-pop that's as catchy as it is avant.

21. "Help I'm Alive," Metric. "Hard to be soft, tough to be tender." Indie vet Emily Haines and her Canadian quartet's polished rock-candy sound is ready for the mainstream, if the mainstream still exists.