Is there room for great soul singers in a post-vocal world? Over the past 10 years, pop voices have gotten thinner and tinnier with Auto-Tune and other production techniques. These days, even Mariah Carey wants to sound like Britney or Rihanna. So where does that leave Mary J. Blige and Alicia Keys, owners of the most distinctive and powerful lungs in the business? These New York soul divas have kept thinking big — by 2007, when you heard Blige's "Just Fine" or Keys' "No One" on the radio, they made the other singers around them sound like yapping Chihuahuas.

Both Keys and Blige have tested the waters with singles where their voices get heavily processed — Blige's "The One" and "Stronger," Keys' "Doesn't Mean Anything" — and it's no coincidence that these singles fell short of the Top 40. Mary J., the queen of hip-hop soul, going Auto-Tune? Isn't that like making the Top Chef cooks do a microwave-pizza challenge?

But Blige's experiment works in the context of her album. One of the reasons fans get so obsessive about Blige is that she wrestles with self-doubt, pushing herself to prove she's good enough, long after her music settled that question for everyone else. So it makes sense for Blige to try on some new outfits — in the fantastic Stargate/Ne-Yo jam "I Feel Good," she flashes the robot-voice ostinatos like a new pair of stilettos. When she sings, "Tipping in my heels with such swagger/Fellas, how are you?" she could be talking about the production. But she also goes for the misty blue-soul grit of "Kitchen" and the Precious theme, "I Can See in Color." The queen sports a new look or two, but those aren't the only items in her wardrobe.

It's different for Keys, because unlike Blige, she's never made a drama out of self-doubt — her cocky assurance is part of her charisma. People loved "No One" because it sounded like nothing else out there at the time — a grown woman emoting with a grown voice, full of low-register warmth and depth. On The Element of Freedom, the production compresses her voice, making it sound a lot less like her, especially on the ballads. Even a great tune like the breakup blues of "Love Is Blind" can make you a little hungry to hear Alicia Keys sing it.

The superb Prince hommages, "Try Sleeping With a Broken Heart" and "This Bed," are experiments that pay off big, submerging Keys' pipes in unabashed 1980s synth cheese. She has less success with "Put It in a Love Song," a Beyoncé-Swizz Beatz collabo that could have been called "Single Ladies 2: Put Another Ring on It." The payback should have been "Distance and Time," a gorgeous anthem that fuses Beyoncé's "Halo" with the Beatles' "Let It Be," except Keys' voice gets quashed in the booth.

Only a stick-in-the-mud would blame these ladies for trying on the latest thing: What's truly noteworthy about these albums isn't their failed moments but the sizzle from the experiments that takes them somewhere new, seeing what the latest studio effects can do for their wonder-of-nature vocals.