Keith Richards fans have been hard at work sleuthing out the answers to riddles posed by his current viral campaign, and all of us get to reap the rewards.

As previously reported, Richards is unlocking a handful of tracks from his new solo LP, Crosseyed Heart, by asking fans to track down a series of commemorative plaques that are being set up in London and Southwest England, each one “celebrating a site of significance to the Rolling Stones guitarist’s life.” Each plaque has a unique password, and once that password is submitted to the Crosseyed Heart website, a new song from the album is being made available.

The first track, “Amnesia," was unlocked after fans submitted the password on the plaque located at Richards' old house on Spielman Road in the Dartford section of London. According to ABC News Radio, the second plaque — unveiled Aug. 24 — was at 33 Chastilian Rd. in Dartford, where Richards lived when he was a baby. That password has also been submitted, unlocking another new song, "Substantial Damage."

Like "Amnesia," "Substantial Damage" is streaming at the Crosseyed Heart site, where you can also see a map showing the locations of the first two plaques — and lock icons teasing the final two tracks yet to be revealed before the album arrives in stores Sept. 18. Check out both songs, and keep an eye on Richards' Facebook and Twitter feeds for more updates on the campaign.

As Richards told the New York Times in an interview published yesterday, he intends to play a few live dates in support of Crosseyed Heart, but he also has an eye toward the next Rolling Stones album, which he hopes will start coming together as soon as they finish their next round of tour dates.

"A lot of the earlier records we made were in between tours. We’d come straight off the road and go straight into the studio, which is why some of those records have so much bounce and hit on them — the energy," he explained. "We’re playing South America in February and March, and I would like to get in the studio around April or May next year. It’s been too long. They need to record. I can feel something in my bones saying we have to record. And maybe [Crosseyed Heart] will be a little kick up the arse."

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