Something seemed fishy when the Twitter account for Fleet Foxes (presumably authored by singer Robin Pecknold) posted this on Saturday: “I would be stoked if I lived in Phoenix.” Few people outside of Phoenix ever have uttered those words, so it made more sense when Pecknold followed with this nugget: “Phoenix comment was foreshadowing.”

It didn’t take much to start sniffing out the clues on the Twitter trail, but when Sub Pop announced a batch of new dates for Fleet Foxes with the Walkmen on Monday and Phoenix was not on there, I went straight to the source (and got a not-so-cryptic reply). By the end of the night, our pal Drew found the smoking gun (only for it to disappear shortly thereafter).

Nevertheless, it’s official now: Fleet Foxes, Bon Iver and the Walkmen will unite on Sept. 15 at Comerica Theatre for one of the beardiest shows you can imagine in another Stateside Presents coup.

With the new Bon Iver album out today, Justin Vernon is everywhere – from Fallon to Colbert to Best New Music status for the 9.5-rated LP.

Fleet Foxes garnered similar praise last month for Helplessness Blues, so you can see what a stir this show will cause.

I’ll try not to be one of those snobs who brags about seeing them before they hit it big, but, well, I did see Fleet Foxes in March 2008 in the cozy confines of Modified, a venue/crowd Pecknold praised in a tour diary at the time. (His seated, microphone-less version of Oliver James was pretty stunning.)

Meanwhile, Bon Iver is back after playing Mesa Arts Center on Sept. 29, 2009.

Tickets for this three-headed extravaganza go on sale Friday.

• Fleet Foxes | Helplessness Blues
• Bon Iver | Calgary