by Christina Aguilera

(MTV)

Dear pop culture: Seriously, no more robots. The whole idea is just dead, and Aguilera's performance here banged its last nail. In truth, the sell-by came a while ago, with the Black Eyed Peas, but watching Aguilera's half-assed Metropolis swipes put the smell in the room for good. It's one thing to make a great fluke by swiping Beyoncé's moves (even if I ultimately love "Ain't No Other Man" even more than I do "Crazy in Love"), but Aguilera's new stuff just sounds ground-out, great pipes or no pipes. And no, a glowing, blinking heart positioned atop your crotch does not qualify as showing us you're really human.

by Janelle Monáe feat. Big Boi

(Atlantic)

Whose fault is this latest robot wave, anyway? Surely Kanye gets some credit/blame for making nice with Daft Punk in '07; maybe Andre 3000 started it when he stopped simply calling himself Dre. That's a parlor game that can last hours. I didn't like Janelle Monáe's Metropolis EP when it came out in 2008, but now, well into our current state of pop robo-overload, it's at least clear that she was creating herself rather than following a pack. That doesn't automatically make anyone a great artist, but it does set a person up as potentially being one. And in its way, "Tightrope" delivers: It's a bionic variation on a mid-'60s James Brown number, every cue hit perfectly. But I don't love it so much as admire it a lot; its skill and ambition are a little stagy by me. But you bet it brightens up the radio.

by Big Boi feat. Andre 3000 and Sleepy Brown

(MP3)

So would this, if radio were to play it. While that's certainly not out of the question, given that this is basically an OutKast record under another billing, it's not the priority for Big Boi's new album on Def Jam, which doesn't include this song because Jive—OutKast's label—won't allow songs that also feature Andre 3000 to appear on another label. Two years after "Royal Flush" proved just how badly rap missed the pair working together, this is more modest musically: live-played, heavy-footed synth-funk-rock with the two MCs rhyming smartly about long-term relationships, especially Andre, who comes up with the best sex simile in a while: "Like we work at IKEA/Test every piece of furniture to see if it is stable."