The sound made by these young choristers is a "cross" between easy-listening pop and traditional cathedral choral. 

There is a medieval and a modern edge to the work, How Good It Is.  It could be described as post-modern musical neo-Gothic with strong overtones of tradition. It is transcendent and beautiful.

So it is difficult to believe this comes from the same place as heavy metal classics such as Paranoid, Iron Man and Children of the Grave.

Legendary Black Sabbath lead guitarist and songwriter Tony Iommi has written the choral work for Birmingham Cathedral to "give something back" to the city of his birth.

Iommi, a true "Brummie" who grew up in Aston and was raised Catholic but rarely attended Mass, worked with Catherine Ogle, Dean of Birmingham and a long-time friend, on the five-minute arrangement.

The aim is to celebrate peace, harmony and the Cathedral's role in the heart of the city.

Ogle wrote the lyrics, based on Psalm 113.

Iommi, credited as founder of heavy metal music and currently on "The End" world tour with Black Sabbath, has recently been told he is free of cancer after a long battle. The band has decided to call it a day, however, and they will perform their last gigs in their home city, at Birmingham's Genting Arena on February 2 and 4.

Iommi said: "It's great to be involved with the Cathedral and doing something for it. When Catherine mentioned it, it felt like a nice thing to do, to be able to give something to the city."

He admitted the choral work is a departure from his more usual style.

"It's just a little bit different to Sabbath. We've done instrumental work before with orchestras and it's something I enjoy doing. It's completely different from any of the heavier stuff. This is a completely new piece of music and I'm really pleased with it." 

The heavy industrial heartland of Birmingham and surrounding towns such as Sandwell and Dudley, once famed for steel works and car factories such as Lucas and British Leyland, were a big influence on the heavy metal rock music pioneered by Black Sabbath.

"So much has changed," said Iommi. "The city is hard to recognise these days. There's so much building work going on, it's really great that the city is expanding and offering people more to do here. It's different from my day. It's great to know after all these years we've been recognised in our city. It's something we're really proud of."

Iommi also said it was a misunderstanding to imagine Black Sabbath had ever been Satanists.

"People used to think we were Satanists but we weren't. The songs were the opposite and all about the dangers of black magic and Satanism. The closest we came was Black Magic chocolates!"

Ogle, who is soon to leave Birmingham to become Dean of Winchester, said in a press release issued by the cathedral: "Tony and I were introduced by a mutual friend and we discussed a possible music collaboration in the future. Then, when Tony was unwell, we got to know one another better when I began to pray for him and kept in touch with Tony and his wife about his health."

It comes soon after the cathedral celebrated its 300th anniversary.

"This is a most wonderful gift Tony offered to the cathedral," said Ogle.

"Tony has a huge fan base in the city. The cathedral is here to serve everyone so we want to connect with them too. The words come from scripture and are really positive about people living together in peace and harmony. This is what Birmingham is all about.

"Birmingham is a fantastic opportunity to demonstrate how such a diverse group of people can live together in peace. That's what we all want. Working with Tony and bringing together such different musical styles is a really good illustration of that.

"It's wonderful when a son of this city, who has had tremendous success, wants to give something back. That he wanted to do that through the Cathedral is very touching."

Prog rock star Rick Wakeman was among those who tweeted in praise of the new choral work:

Lyrics for How Good It Is Inspired by Psalm 133

How good, oh how good... How good it is

Where friendship dwells How good it is

 When kindred live
 In peace and love

How good it is
 When strangers meet
 And find a home
 How good it is, so good....
 This is home, this is home...
 Our city, God's city, our home....
 So good, so good, together, so good...