Now we have evidence that suggests at least one singer will be Joan Jett. Today @FooFighters Instagrammed a photo of instruments, presumably from event rehearsals. It shows Krist Novoselic’s bass, Pat Smear’s guitar, Dave Grohl’s drumkit ... and Joan Jett’s Melody Maker. Check it out below.

This would make sense.  Joan has played with the FOO FIGHTERS ... DAVE GROHL'S other band ... several times, including once on "Letterman".  

Speaking of Nirvana and Kurt Cobain, there's a movie coming out called "Soaked in Bleach", about the conspiracy theories surrounding Kurt's death ... specifically that COURTNEY LOVE had him murdered so that she could inherit his money.