Josh Groban dreams of one day recording his own version of classic song Unchained Melody, although it could be years before he feels up for the "challenge".

The You Raise Me Up hitmaker recently checked off another bucket list track by recording The First Time Ever I Saw Your Face, made famous by Roberta Flack, for his latest covers album, Harmony, but he has revealed there's one famous record he has always hoped to revamp.

"I have a bucket list song that I have not yet recorded, which is Unchained Melody, that I want to sing at some point...," he shared on Today. "I think it's probably one of, if not the, best love songs."

However, Groban insisted it's not a cover he will be rushing into, because he wants to find the perfect way to make it his own, while also paying homage to The Righteous Brothers, who turned the Todd Duncan tune into a big hit in 1965.

"It's one of those ones where you know the original so well, and that's a big challenge for a singer, what on earth are you gonna do that both honours the original and also allows you to do your own thing to it?" he said, admitting it's the same reason he also waited a while to record The First Time Ever I Saw Your Face.

"So that's why sometimes I wait a couple decades, because I just don't feel ready! It'll happen, it'll happen," he added.