Rock legend David Bowie spent two years working in secret on his upcoming album, according to his longtime producer Tony Visconti.

Fans had no idea the reclusive star was making music again until Tuesday (08Jan13), his 66th birthday, when he unveiled new single Where Are We Now? - his first release in a decade.

Visconti, Bowie's collaborator over the past four decades, now reveals the singer couldn't stop smiling as they recorded his comeback album The Next Day, although he admits they worked at a slow pace.

Visconti tells the Bbc, "He smiles a lot. During the recording he was smiling all the time, he was so happy to be back in the studio. He still has that power in his chest, in his voice. He still has it...

"We never spent more than two to three weeks at a time recording. Then we might take off as much as two months. We usually work on about one or two songs in an afternoon and we'd whip them up to shape where they'd sound like great rock tracks... This is actually the same way I'd been working with him since The Man Who Sold the World. He hasn't really changed in his approach."

The producer also dismissed rumours that Bowie's absence from the spotlight has been down to ongoing health issues, adding, "David is extremely healthy. He's rosy-cheeked... He's a very healthy man, I can assure you. I couldn't explain why I know that, but I worked with a very healthy David Bowie in the studio and a very happy David Bowie in the studio."

The duo first joined forces in 1969 on Space Oddity, and together they created classic Bowie albums including Heroes, Lodger and Young Americans.

The Next Day is due to hit shelves in March (13).