Richard Hickox, described as "one of the world's leading conductors", has died from a suspected heart attack aged 60.
Hickox died yesterday in his hotel room in Cardiff after a recording session in the city, his publicist said.
He was due to conduct English National Opera's new production of Vaughan Williams's opera Riders To The Sea, opening this Thursday.
The conductor is survived by his wife, the mezzo-soprano Pamela Helen Stephen, and his three children, Tom, Adam and Abigail.
Hickox was musical director of Opera Australia, associate guest conductor of the London Symphony Orchestra, founder and music director of the City of London Sinfonia, co-director of the period instrument group Collegium Musicum 90 and conductor emeritus of the BBC National Orchestra of Wales.
Stephen Lumsden, managing director of Intermusica, and Hickox's agent for more than 20 years, said: "The shock of Richard Hickox's sudden and unexpected death will resonate right around the globe and has robbed the music world of one of its most popular and respected musicians.
"It also takes away from his beloved family a deeply devoted husband, father, son and brother.
"Literally thousands of musicians who were touched by his talent, energy and that remarkable generosity of spirit of his will feel that loss as well.
"Richard never wavered or faltered in his commitment and support for others, even when faced with the most daunting challenges.
"His ability to inspire the best through his passion for the music he conducted created countless memorable performances in the concert hall, on the opera stage and on disc.
"His championing of British music and his international successes, particularly in Sydney, as well as his legacy of hundreds of recordings across the whole spectrum of repertoire will remain for many years to come.
"All those who knew him will feel deeply for his wife Pamela and his three children, to whom we offer our most sincere and heartfelt condolences."
Hickox was appointed musical director of Opera Australia in 2005 and recently had his contract extended to 2012.
He regularly conducted the major UK orchestras and appeared on numerous occasions at festivals such as Aldeburgh, Bath, Cheltenham and the BBC Proms.
He was awarded the CBE in the Queen's Jubilee Honours List in 2002.
The conductor could also boast a discography of more than 300 recordings.
In 2006 he received his fifth Gramophone Award - the Editor's Choice award for his recording of Stanford sea songs on Chandos with Gerald Finley and the BBC National Orchestra and Chorus of Wales.
In 2001 he was awarded Gramophone Record of the Year and Best Orchestral Disc for his recording with the London Symphony Orchestra of Vaughan Williams's Symphony No 2 in the original version, which also received a Classical Brit Award.
His clutch of gongs also included two Royal Philharmonic Society Music Awards, the first Sir Charles Groves Award, the Evening Standard Opera Award, and the Association of British Orchestras award.
He was an Honorary Fellow of Queens' College Cambridge, where he was Organ Scholar, and was awarded a Doctorate of Music at Durham University in 2003.
Hickox had a long connection with the Royal Opera, Covent Garden, where this season he was due to conduct L'Elisir d'Amore and The Beggar's Opera.
Past productions there included Paul Bunyan, Billy Budd, Tales Of Hoffman, Mitridate and A Midsummer Marriage.
He also conducted Billy Budd at the Vienna State Opera, Washington Opera and in Cologne; Salome, I Capuleti e I Montecchi and Rigoletto in Los Angeles, and many productions for English National Opera.
In 2004 BBC2 televised his Turn Of The Screw.
He was music director at the Spoleto Festival in Italy for five years, where his productions included Rosenkavalier, Cunning Little Vixen, Prokofiev's War And Peace, and Menotti's The Consul.
Hickox conducted many of the leading orchestras in Europe, Japan and North America, including most recently the Bavarian Radio Symphony, Leipzig Gewandhaus, Orchestre de Paris, New York Philharmonic, and Philadelphia Orchestra.
He was a regular guest with the Philharmonia Orchestra, with whom this year he undertook a series of some 20 concerts, presenting the entire cycle of Vaughan Williams' Symphonies at the Royal Festival Hall and across the UK to mark the 50th anniversary of the composer's death.
Tributes flooded in for the conductor.
Roger Wright, Controller BBC Radio and Director BBC Proms, said: "I am deeply saddened by this unexpected news.
"The classical music world has lost a major figure whose musicianship and enthusiasm endeared him to audiences in opera houses and concert halls throughout the world.
"He was a wonderful colleague.
"Richard was a magnificent conductor and did wonderful work with many BBC performing groups, particularly his wonderful spell as principal conductor of the BBC National Orchestra of Wales.
"He was a frequent conductor at the BBC Proms and his extraordinary recorded legacy is regularly heard on Radio 3, not least his powerful advocacy of British music. He will be much missed."
David Murray, Director BBC National Orchestra and Chorus of Wales, said: "All of us at the BBC National Orchestra and Chorus of Wales are shocked by the news of Richard Hickox's sudden death.
"He was working with us yesterday on a CD recording in the Brangywn Hall Swansea, when he was suddenly taken ill.
"Our thoughts at this time are with Richard's mother, his wife Pamela, and their children.
"As well as losing an inspiring conductor, we have lost a great friend and supporter of the Orchestra and Chorus."
Menna Richards, Controller BBC Wales, said: "I am deeply saddened and shocked by the news of Richard Hickox's sudden and untimely death.
"All of us at BBC Wales are proud that he took on the position of the first conductor emeritus of the BBC National Orchestra of Wales following periods as guest and principal conductor.
"He was an inspirational musician and the BBC National Orchestra of Wales gave some extraordinarily powerful performances with Richard as conductor.
"He will be badly missed and our thoughts are with his family at this profoundly sad time."