The mezzo-soprano, who had gained an international reputation for her singing, was found outside a house in Keyingham, near Hull, just before 8am on Tuesday.

The 36-year-old had only recently started performing again following major heart surgery and the last performance she gave was with the London Theatre Voices alongside the Driffield Male Voice Choir (DMVC) at Driffield Methodist Church on Saturday night.

President of the Driffield Male Voice Choir Alan Binnington said: "The whole affair is very, very sad and just a few days after she gave a stunning performance in Driffield with the choir."

Peter Dix, DMVC honorary secretary, said Miss Black's performance on Saturday was "absolutely fantastic," adding: "Ironically the last piece she sang was called Amen. Her voice floated above everybody else, it was just amazing."

Mr Dix said the choir was shocked and deeply saddened to hear the news of her death, describing it as "an absolute tragedy".

DMVC musical director Ian Cockerline knew Miss Black in her younger days when she was a regular participant in a Cottingham music festival and said her death was a sad loss, especially as she was just getting back into her stride.

"It's just something you don't expect and it's such a loss. The suddennes of it is so saddening," he said.

Miss Black, who grew up in Hedon, studied at the Royal Academy of Music and toured with the European Opera, as well as spending seasons at Glyndebourne and with English National Opera.

She gave many concerts and recitals in the UK, appearing at Hull City Hall and singing regularly at Hull FC matches at the KC Stadium.

A founder member of the London Theatre Voices, a quartet of friends who met while singing for the English National Opera, she was known as the star of Classics in the Park, held at Brantingham.

In a statement issued through the police, Miss Black's parents thanked the local community for their support at such a difficult time and asked to be left in peace while they came to terms with their daughter's death.

Miss Black underwent surgery in June at the Royal Brompton Hospital after routine tests revealed she had a defect of the aortic valve that results in the formation of two cusps instead of the normal three.

For three months she was unable to sing but made her comeback in October with a performance at Toll Gavel Methodist Church in Beverley.

Humberside Police were called by the ambulance service following the discovery of a body near Mill Nurseries, Main Street, in Keyingham.

Det Insp Colin Waddington said: "Police are not treating her death as suspicious but it is still unexplained.

"We have a duty of care to Amy, her family and the coroner to investigate her sudden death and to ascertain what happened."

A post-mortem was carried out on Wednesday and pathologists are currently working to find out the cause of her death, which may take several weeks.