Queen say Adam Lambert has ''one voice in a billion''.

The legendary rock band - featuring original guitarist Brian May and drummer Roger Taylor - have been touring with the former 'American Idol' star in replacement of the late Freddie Mercury, who died in 1991, and are constantly surprised by his vocal abilities.

Brian told iHeartRadio: ''He's extraordinary. It speaks for itself, his voice. That's one voice in a billion.

''Adam can do things which really I have never heard anyone else ever do in my life.''

Brian and Roger played with Adam for the first time on the final of 'American Idol' in 2009, when he sung Queen's 'We Are the Champions' and was eventually runner up to KRIS ALLEN.

Brian added: ''We have a chance to do great things with Adam Lambert. He really is a wonderful foil for us, so it's a kind of gift from heaven, really. It's a lot of fun, too. He's nice to work with. He's fun and light and he doesn't have any airs and graces, and you know, he just gets on with it, and we feel like a family. It's nice.''

Brian, 66, also played down the idea Adam is a replacement for Freddie, as he sings the songs in a different way.

He added: ''It just works with him. It feels comfortable and nice, and challenging, also, because he puts different interpretations on the songs, so it gets us to play a little differently. So, it's nice, it's alive.''