The producer told the Herald Sun that there was not yet a release date for his and Chad Hugo's follow-up to 2003's The Neptunes Present... Clones.
Williams said: "This new Neptunes record we're working on right now is vicious. It's definitely harder - it totally demands sweat."
Asked to compare Neptunes to his and Hugo's work as part of N.E.R.D, he added: "Music is music, but with N.E.R.D we put more of our personality into it, that's just us being us.
"With Neptunes we produce for a lot of people so we allow space for their personalities, for them to be themselves, and our music sort of commandeers the direction a bit."
Discussing his current work, Williams said: "The new stuff has been going well. We've been playing with Gorillaz on the road so it has been fun. They are awesome - there were so many people on stage it was like Parliament psychedelic up there.
"I've just been all over the place from project to project... and there's another Despicable Me [soundtrack]. We've also got some stuff going on with Madonna."