"When we were making our first few records, we really didn't know what the fuck we were doing."

Dan Auerbach made that blunt -- and some might say blasphemous -- statement last week by phone from New York, following a particularly momentous few days for his Akron, Ohio-reared, smoking, snaking blues/punk/psychedelic band the Black Keys. He and his bandmate since childhood, drummer Patrick Carney, had just come off of playing Madison Square Garden with Pearl Jam and "The Late Show With David Letterman."

The morning of our interview, they debuted at No. 3 in Billboard with their sixth album, "Brothers," their best showing to date. Most reviews also deemed it their best effort yet. Auerbach certainly didn't argue.

"We didn't know how to write a song back then," continued the singer/guitarist, 31. "We were just starting to get used to playing our instruments. That was fun, and it's fun to hear it because it is so ramshackle and immediate. But we've grown up. We're not the same people -- although we really did have just as much fun making this record. We liked the challenge of it, most of all."

You can hear the challenges rise and tumble away on the new album, which was partially recorded at the legendary Muscle Shoals Studio in Alabama. Instead of the scorching riffs and bursting beats of past Keys discs -- is there a Keys fan out there who doesn't air-guitar "10 A.M. Automatic" on a weekly basis? -- this one features more slow-grinding grooves, introspective songs and cool bits of soul.

"Brothers" followed a yearlong hiatus for the Black Keys. Auerbach toured behind his first solo record ("Keep It Hid") and produced some younger bands (Hacienda, Cadillac Sky). Carney put together a new band called Drummer (in which he played bass) and split up with his now ex-wife (hints of which permeate "Brothers"). The duo also made the "Blakroc" album with Roc-A-Fella co-founder Damon Dash and rappers Mos Def, Ludacris and RZA.

As Auerbach explained, these diversions helped clear away the new paths on "Brothers."

Q: So a little time off did the Black Keys a world of good?

A: Yeah, definitely. In terms of songwriting, I started to open up and have fun on my solo record. And then the "Blackroc" record had a big effect, because we started all those songs for the most part with bass and drums instead of guitar and drums. We had so much fun doing that, we carried it over to "Brothers." I think it reinforced the groove on this record.

Also, working with other people definitely helped us realize how effortless it is for Pat and I to work together. It really is. We could make a record every week.

Q: How big an impact was recording at Muscle Shoals?

A We had a good time, but Pat and I could've made that record anywhere. There was nothing special about the studio or the equipment used. It was run-of-the-mill stuff. We had a super-talented engineer, Mark Neill, but the connection that Pat and I have was the key.

Q: Is it fair to say you were more focused on vocals than guitars this time?

A: I'd say it was songs over arrangements. There's more of an overall sound and feeling we're trying to get across. There's not any solo instrument, it's all one song. I was really happy with all the lyrics and really wanted them to sound special.

Vocally, I definitely tried things I hadn't done before. I didn't really think about it, I just did it. "Everlasting Life," I sang that in falsetto, and I hadn't ever sung in falsetto before that day. That was done in one take, too. This record was magical in that way. It just came together and happened on its own.

Q: Did the bass and keyboards force you to add a couple extra musicians on tour?

A: Yeah, we really like the arrangements on the record. We wanted to keep them similar and not have to strip them down. So we found a couple of like-minded slackers who will play a few songs with us every night: Leon Michels on keyboards, and Nick Movshon on bass. They grew up together playing music just like Pat and I, and had a great group called the Mighty Imperials. They're in the same headspace as us, so it's not like we're hiring some hot L.A. session players.

Q: Any hesitation to mess with the fabled Black Keys two-man formula?

A: Not at all. You know, we've had creative control over everything we've done, since we started. If we want a couple guys along to play some shows with us onstage, I don't think it's weird at all. We're not some kind of two-piece novelty act. We're a band. Green Day is known as a three-piece but tours as a five-piece, and no one asks them about it.

Q: How did Minneapolis luck into two gigs at First Avenue instead of one at a bigger place?

A: I think it's because we would have to move up to a theater. We hate playing sit-down places. It's always kind of a bummer. We like it when people can jump around. Theaters are good for bands who play for 2 1/2 hours and fans can take a break and sit down, but we don't let up.

We love the Twin Cities. There's a really great guitar shop there, Willie's. For a while there, I think I had them on speed-dial. I actually bought a Fender VI there, which is like a baritone guitar. We used it on the record we did with Danger Mouse. We were like, "God, we gotta get this," so Pat and I split the cost. Now we each have joint custody over it.