Up until recently, it would have appeared that Pink Floyd's founding drummer, Nick Mason, was semi-retired from music. It has been four years since the release of Floyd's last studio album, The Endless River. With a few rare exceptions—such as when he guested at Roger Waters' 2011 The Wall show, and appeared with Ed Sheeran to play the closing ceremony at the 2012 Olympics—Mason hadn't performed in public for an extended period of time; Pink Floyd's last major tour was for The Division Bell album nearly 25 years ago.

That recently changed for the 74-year-old drummer, the only member of Pink Floyd who has performed on all of the band's studio albums. This past May, he played four intimate concerts in London with his new band, Saucerful of Secrets. The setlist for those shows concentrated on Pink Floyd's early years—especially songs with founding singer/guitarist Syd Barrett – more than the commercially successful post-Dark Side of the Moon material. Following those gigs, Mason and Saucerful of Secrets— which consists of guitarist Lee Harris, longtime Floyd touring bassist Guy Pratt, Spandau Ballet guitarist Gary Kemp, and keyboardist Dom Beken—will embark on an 21-date European tour starting Sept. 2 in Stockholm.

The impetus behind Saucerful of Secrets came from a conversation between Harris and Pratt on why Mason hadn't done something musical lately. “If it had just come from Lee,” Mason tells Billboard, “I probably would have thought, 'Hmmm, not really.' But the fact that I’ve worked with Guy on and off for the last 30-odd years, I thought, 'Well, if Guy’s involved, this could really work.' And then Gary joined in saying he’d love to do something. Suddenly there was an actual sort of focus on how this could work. We went and did a couple of days’ rehearsals. Everyone came away from it absolutely buzzing.”

Among the numbers Saucerful of Secrets had played at the recent London shows included “See Emily Play,' “Arnold Layne,” The Nile Song,” “Bike,” “Set the Controls for the Heart of the Sun,” and “Obscured by Clouds”—songs that either Pink Floyd hadn't performed during arena tours or never played live at all. “I'm sure we did play ['See Emily Play'] live when Syd was in the band,” Mason recalls. “Once Syd had gone, the move was to try new material so David can sing things [without] having to really recreate Syd for an audience. I would think we did play 'See Emily Play,' because at the time we were on Top of the Pops. We would have absolutely been required to play that whenever we were going out on the road at the time.”

Mason acknowledges that re-learning the older material wasn't easy at first. “Being an eternal optimist, I thought it would just come straight back to me. Sadly, I was wrong. Once you start examining Syd’s work carefully it’s quite often more complex than you expect. It's not necessarily written like so many pop songs with an eight-bar section and the middle eights and whatever. It's quite often a completely different set of bar counts to what you're expecting. And that in a way was fun and challenging to get at the feel of the song, but not necessarily feel that we had to sound exactly like Syd or like David or whatever.”

The positive reaction to the U.K. shows even caught Mason by surprise. “I think we found a niche for ourselves,” he explains, “which is to do something that is not being done by everyone else, by the tribute bands or by Roger or David. It's a real return to some of the improvised sections and the atmosphere of the songs. The tendency in this day and age is to try and recreate things perfectly. We bring imperfection.”

The name of the band, Saucerful of Secrets, is obviously a reference to the title of Pink Floyd's second album, A Saucerful of Secrets, released in June 1968. It is a significant record in Floyd's history in that it was the last album Barrett played on and the first to feature David Gilmour. “It's a quick way of explaining to people what we're doing,” Mason says of his new band's moniker. “What I didn't want to get caught up in were a lot of people going, 'Well, why don't you play "Comfortably Numb"?' or 'Why don't you do something from The Wall?' I think the name itself indicates where we are and what we're doing.”

The upcoming European tour comes as Rhino/Parlophone is releasing on Aug. 31 a 3-CD set, appropriately titled Unattended Luggage, featuring Mason's solo recordings that had been previously out of print for decades. The first of them, 1981's Fictitious Sports, a jazz and progressive rock-sounding record, is unique in that it features songs written by composer Carla Bley and lead vocals by Soft Machine's Robert Wyatt. “I loved that record,” Mason says. “I think the thing that was sort of confusing for people is that it's a Nick Mason solo album. It’s nothing of the sort, of course. What I actually ended up doing was taking the opportunity to let Carla loose on some very funny songs and brilliant brass arrangements.”

In the mid '80s, Mason collaborated with 10cc guitarist Rick Fenn on a couple of studio and soundtrack projects, including the very polished and synth-oriented Profiles (which features a guest vocal by Gilmour on the track “Lie for a Lie”) and the 1987 Donald Cammell film White of the Eye -- both of which are also included on Unattended Luggage. “The Profiles stuff, I think you know more or less exactly when it was recorded,” explains Mason. “The other album [White of the Eye] could be present-day more or less.”

Depending on how the European tour goes, Mason isn't ruling out Saucerful of Secrets playing some dates in the United States -- something he says his new group would love to do. “What I underestimated was the enthusiasm, not of the audience, but of the band,” Mason says. “Pink Floyd was always enthusiastic, but not like this lot is now. Everyone wants to do everything: 'We want to go to America.' 'We want to go to South America.' 'What about Peru?' (laughs). It's like a travel agency.”

Mason admits to being surprised himself about performing on stage once again. “But I'm absolutely delighted,” he says. “I’m really enjoying it.”