Justin Bieber and Skrillex are working on ''timeless'' music.

The 'Boyfriend' singer and the 'Bangarang' hitmaker collaborated with Diplo on the track 'Where Are U Now' and have reunited again to work on more music together.

Skrillex said: ''We're writing great songs, take all the production away and just break it down to the melody and the vocal ... we're writing really great songs.

''For me, at least, I feel like 'Where Are U Now' was his first step into real songs, almost like timeless songs. No matter what you think about who he is, you can't deny that he wrote a great song and that's what we're doing, and that's what the goal is for this record.''

But the 27-year-old music producer believes the 21-year-old singer took the ''biggest risk'' releasing the track as his first new piece of music since December 2013.

He added to MTV: ''I think he already took the biggest risk releasing his first single in a long time with Diplo and myself, and it had such a great response, and now it's just very freeing because that's what we're chasing after, just making good songs.

''I think that when you hear his voice... there's something that happens. I really like the stuff that we worked on together and we'll see what the world thinks when it comes out.''