The writer of Christmas number one Wherever You Go has composed a new work which features a note six semitones below the deepest note ever written for a choir.

Now the company is embarking on a bass odyssey, placing ads for a singer who can reach the note to allow Paul Mealor's work to be recorded this spring.

Mealor saw one of his compositions included in the Royal Wedding last year, as well as tasting success with the song he wrote for Gareth Malone's Military Wives.

His works are characterised by very low notes, but he has surpassed himself in the new Russian Orthodox-style piece by stretching down to a low E - nearly three octaves below middle C.

It is so deep that it is thought never to have been sung before and is two semitones below the world record holder bass note, a sung F sharp. The lowest note ever thought to have been included in a choral piece until now was a B flat, in Rachmaninov's Vespers.

Mealor - whose Wherever You Go beat X Factor winners to the festive number one - said: "My setting of De Profundis calls for a rich and powerful voice.

"A voice that can not only touch the heart with its sincerity and truth, but also make every fabric of the human body resonate as it plunges into the very lowest parts of the vocal spectrum."

Adverts announcing the talent search will appear in international publications and online, asking "How low can you go? How deep can you sing?".

Singers are asked to send demo tapes, or upload their voices to a website www.howlowwillyougo.com which has been set up.