Cat Deeley explains everything you need to know about Sing: Ultimate A Cappella on Sky 1

Oh, and there's something else rather special about the show. It's presented by Cat Deeley – one of the few British presenters who's managed to crack America as the host of So You Think You Can Dance, a show she's been Emmy-nominated for five times.

Now she's returning to UK screens fresh from LA after a very long absence, and RadioTimes.com sat down with Cat to help explain what's so special about Sing: Ultimate A Cappella:

What is Sing: Ultimate A Cappella?

It's a brand new singing show on Sky1. Over seven weeks, 30 groups will be battling it out to be named the best a cappella group in the UK. "There are no musical instruments, no backing tracks," Cat Deeley tells RadioTimes.com. "There really is nowhere for anybody to hide."

How does Sing: Ultimate A Cappella work?

There are seven weeks of Sing: Ultimate A Cappella – six episodes of heats and one final.

In each heat, five groups of singers have to first tackle 'Medleys' where they must impress the judges with a medley of two songs. They then receive a score for their vocals, musicality, interpretation and performance. The group with the lowest score is eliminated, with the other four groups going through to the second stage: 'Iconic artists'.

This is where the groups must each a perform song by a musical icon, including the likes of Queen and David Bowie. Again they are scored, and the two lowest groups are eliminated.

Finally in each episode there's the 'Showdown'. The last two groups standing perform a 'showstopper' song where they hope to bring their very best performance in order to win a spot in the final.

Over six weeks, six finalists will be chosen and they will head into the final.

"It’s really hard to compare each group, actually," says Cat. "It's one of the things I’ve noticed about the show, and why I like it so much. The diversity of the people that do it – I had no idea there was that many people that sing in a cappella groups, and it’s everybody from university students to gospel choirs to 6ft 5 tattooed, stay-at-home dads and barbershop boys. It’s all encompassing, and it’s a real trend right now. There’s so many people doing it."

Who are the judges on Sing: Ultimate A Cappella?

There are five judges on Sing: Ultimate A Cappella, and although they're not household names they are big figures in the world of music.

"We have judges that maybe the audience wouldn’t necessarily know, but they’re experts in their field," explains Cat. "It means that they can do this thing where they break down every single performance in terms of voices, improvisation, musicality, performance."

Joanna L’Estrange is an arranger, lyricist and choral conductor who has worked for BBC Choir of the Year and judged the International A Cappella Contest. As a vocalist she has also sung with Take That and Sir Paul McCartney, as well as appearing on over 150 film soundtracks.

Ben Sawyer is a founding member of award-winning a cappella group The Songmen, Rachel Mason is a songwriter, vocal teacher and performer and has judged a number of vocal contests including Voice Festival UK.

Meanwhile Carol Pemberton founded a cappella quintet Black Voices 30 years ago, has an MBE for services to music and her niece is MOBO award-winning singer Laura Mvula. Lastly, Aaron Lee Lambert is a star of the West End and is currently appearing in the UK tour of Sister Act.

Who is the house group on Sing: Ultimate A Cappella?

They're called Sons of Pitches (see what they did there?) and Cat told us she thought they were "the cutest, most divine lads on the planet. I kind of want to adopt them all."

Sons of Pitches won Gareth Malone's BBC2 series The Naked Choir back in 2015 and they are Midé, Jamie, Josh, Joe Novelli, Joe Hinds and Joe Belham. That's a lot of Joes.

Joe H says of a cappella: "It’s such a good platform to be musically creative. We do a lot of educational work going into schools and it means people who aren’t, theoretically, musical, will actually give it a go. That’s what’s amazing about it, really."

Who are the musical guests on Sing: Ultimate A Cappella?

Across the six episodes, there are six different musical guest stars. The Vamps will be starring in the first episode, with subsequent weeks featuring Imelda May, Reggie Watts, JP Cooper, Midge Ure and Gregory Porter. The catch for them all is that they have to each also perform a cappella.

"Midge Ure came on, and even he said, after all these years and all the things he’s done he was like 'I was slightly terrified'," explains Cat. "I asked him why he was doing it and he said 'For that very reason. I was slightly terrified, and I’ve never done it before, and I like doing something that scares me a little bit, and I want to tick it off the box.' And I thought 'Ooh! That is really cool!'"

Why is Sing: Ultimate A Cappella different to other TV talent shows like The X Factor and The Voice?

"I feel like our format is different," Cat tells RadioTimes.com. "We’re not so judge-heavy. We’re not relying on celebrities making bold statements and sound bites. It’s more about the a cappella, and about all these different people that literally are probably your next-door neighbour that just have this passion to sing.

"I think it’s a different show although the same audience can still watch it," she continues. "I think that the family could sit at home on the couch and watch it all together and absolutely enjoy it. We’re using all different types of music from all different genres from all different generations. Everything from Rihanna to David Bowie, we’re mashing it all up.

"It’s like Pitch Perfect the movie. Everybody can go to the cinema and watch that and enjoy it. I think that is what makes it really fun for the whole family to watch."

What do the winners of Sing: Ultimate A Cappella get?

The winning group of Sing: Ultimate A Cappella gets the chance to record an album at the world famous Abbey Road Studios and release a single in time for Christmas.

Sing: Ultimate A Cappella airs 9pm Fridays on Sky1