The former Led Zeppelin singer has been concentrating on softer projects, such as his 'Raising Sand' album with Alison Krauss, and his Band of Joy group, but after a recent concert in London, realised he his slipped back into full rock mode.
He said: "That was the great thing about the adventures with Alison, and singing with Patty [Griffin, his partner] and [Band of Joy guitarist] Buddy Miller, that I started singing differently.
"Somebody said to me in London when we played the Forum recently, 'You had your big voice back.'
"I put the big voice away for quite a long time because I thought, we know how to do that. So it was good to get it out again. It's all the same really, you just have to use the right colours for the right picture."
Robert has now formed a new band, Sensational Space Shifters, and is putting together a new album, which he describes as "12 tracks, 11 originals and no sentimental stuff," and was informed by his recently going back to the Mississippi delta where blues music originated from.
He added to the Daily Telegraph newspaper: "I don't know when it was that I first came here. If I said I came looking for Robert Johnson... I was actually just looking for clues. And I found clues.
"When I came here in the 1980s, before the museum was here, when RL Burnside and Junior Kimbrough were still playing, there was still an actual scene for that grinding [blues] stuff, so it was very easy for white kids to get on to that. I suppose that was the last really great flurry."