Mick Jagger has gone in the studio in advance of another round of concert dates with the Rolling Stones, but it's not with Keith Richards. Instead, the flamboyant frontman is sitting in with his younger brother, Chris Jagger.

Mick confirmed his appearance on 'Concertina Jack,' Chris Jagger's ninth solo album dating back to 1973, via Twitter. Chris' most recent album was 2009's 'The Ridge'; his website also mentions contributions to a pair of 1980s-era Rolling Stones projects, 'Dirty Work' and 'Steel Wheels.'

"I'm not a big one for anniversaries,” says Chris Jagger in a statement, "but in the brew ha ha revolving around the Rolling Stones and 50 years, I realized it's 40 years since my first record came out."

Mick will appear twice on 'Concertina Jack,' the title track and 'Diamond and Pearls.' Sessions took place in France, with Stones sideman Bobby Keys and Tim Rees also participating.

The Rolling Stones announced 12 new concert dates this week, in the Asia, the Far East, Australia and New Zealand for 2013, with at least two more to come. Mick Taylor, a member of the group from 1969-74, will appear as a special guest through the tour, dubbed '14 on Fire.'