Back in 2013, Black Sabbath's Tony Iommi and Queen's Brian May discussed doing an album together, and in 2017 that came up yet again.
Now in 2019, the duo have been hanging out once more and listening to some riffs that Iommi appears to have come up with. According to Iommi's Instagram, he and May were "Hard at work ! In search of riffs – and finding about 500 !"
In the May 2013 issue of Kerrang! magazine, Brian May was answering fan questions when one was submitted by Tony Iommi asking:
When are we going to get to work on that album of riffs together? You know what I'm talking about.
May responded:
"Yes, I do know what he's talking about, and I'm very, very keen. The record he's talking about what supposed to be a secret, but I guess he's blown it now."
May was astounded by the amount of riffs Iommi, aka the Godfather of heavy metal, has in his arsenal. May wanted to release a compilation of the riffs and let musicians compile their own songs out of them.
"The idea was to put all these riffs out in some form so that people could build their own songs from them. You could make your own music with Tony Iommi on guitar!"
Iommi told Eon Music in 2017 that May was just over his house, and the two were talking about doing an album.
Brian came up to my house a couple of weeks ago, and we started talking about it again, but it’s quite possible. We’d like to do it, but now he’s going on tour. But yeah, I’d like to do something with him.
Obviously this is all speculation at this point, but these two have been talking about doing a record together for long enough that it might actually happen.