Britney Spears is brimming with creative ideas on the music front, according to will.i.am -- with whom she just collab'd for her latest track -- and he says there's good reason to expect more music from her.

The Black Eyed Peas frontman's joining us "TMZ Live" on the heels of his and Britney's new single, 'Mind Your Business,' which just dropped Friday. It's the second song Britney's been featured on since her conservatorship ended.

The track came as a surprise to many -- Will acknowledges they actually recorded most of the song back in 2013, but says this was the perfect time to finish production and release it.

That's because of the song's message -- on the surface, it's all about Britney's storied history with paparazzi, and her general feeling of losing all privacy ... but Will adds, it's not just about her.

It's interesting ... he says everyone's personal life is invaded these days, which makes this an issue that transcends celebrity.

As far as any future projects together -- this is already their 4th collab -- Will says it's a bit TBD ... but he does tell us Britney is still very much invested in music -- proven, he says, by the suggestions she was making while they were working on "Mind Your Business."