What do Elvis Costello, Ben Harper, Dr. John, Grace Potter, Steve Winwood, and Dave Matthews have in common? Well, apart from the fact that they’re all certified rock stars in their own right, they each sang lead on a track on Shout!, the new album from American blues-rock/jam act Gov’t Mule.

The idea for the monumental double disc—to record two versions of each of its 11 songs, one with Mule main man Warren Haynes singing, the other with a special guest at the mike—came about “gradually and organically”.

“We had already decided on the songs,” explains the band’s singer, guitarist, and main songwriter from his home in Manhattan, “and were pretty far along into the recording process before we came up with the concept. It started with ‘Funny Little Tragedy’, and then ‘Scared to Live’, and then ‘Stoop So Low’, and once we decided to have guests on those we thought, ‘What about making a whole bonus disc and having a different guest for each song?’ ”

After running through the blues/groove-based but stylistically varied Shout!—which also boasts lead-vocal spots by reggaeman Toots Hibbert, Jim James of My Morning Jacket, Vintage Trouble’s Ty Taylor, Myles Kennedy from Slash’s band, and former Deep Purple member Glenn Hughes—it’s hard to pick a standout track. When asked about his own faves, Haynes points to the three previously mentioned songs—which feature vocals by Costello, Hibbert, and Dr. John, respectively—as well as “When the World Gets Small” (Winwood) and “Capture” (James).

“As clichéd as it sounds,” he says, “I really love all of them. Basically I made a list of each song and what singer other than myself I would really love to hear sing it, and then started makin’ phone calls. The response was overwhelming, and I think each singer sounds perfect for the song they were asked to sing.”

Shout! is Gov’t Mule’s debut release on Blue Note Records, the fabled jazz label that’s been around since 1939. The connection to Blue Note was first made when Haynes took part in a PBS blues special taped at the White House in February of 2012. Besides music legends such as Jeff Beck, Mick Jagger, B. B. King, and Buddy Guy, recently named Blue Note president Don Was showed up, and a “casual conversation” between him and Haynes led to the signing four months ago.

Speaking of lucrative deals conceived in the corridors of power, politics is one subject Gov’t Mule has been known to dabble in at times. A song like 2006’s “Mr. High & Mighty”, for example, sounded like an obvious indictment of then-president George W. Bush’s warmongering ways. So one wonders if the recent U.S. government shutdown might inspire a tune or two from Haynes.

“Well, there’s a lot going on right now that tends to inspire more political writing,” he concedes. “And actually, although the main meaning of the title Shout! was to pay homage to all the great rock singers, it also has a double meaning. If you look at the album art, it’s all propaganda-type artwork, and the message behind that is ‘Everyone has a voice. It’s time to use it.’ ”