Sir Stephen Cleobury, who directed the choir at King's College Cambridge for nearly four decades, has died aged 70.
The British conductor, organist and composer presided over the world-famous Festival of Nine Lessons and Carols broadcast live on BBC radio on Christmas Eve.
He also conducted a number of other ensembles including the BBC Singers.
The Provost at King's College, Professor Michael Proctor, said it was a "truly sad day".
"The college community, and indeed many around the world, are mourning his passing with a profound feeling of loss," he added.
Sir Stephen died in his hometown, York, on Friday after a long illness, King's said.
The college will host a memorial service for him later in the academic year.
Sir Stephen retired as director of music at King's just two months ago after 37 years in the role.
The musical director helped to build the world-renowned Christmas Eve carol service held in King's College Chapel, founding the tradition of an annual new commissioned carol.
Since 1984, this has made an invaluable contribution to contemporary carol writing, according to the college.
The service is broadcast live on Radio 4 and the World Service on 24 December. A separate pre-recorded service Carols from King's is broadcast at Christmas on BBC television.
Sir Stephen also introduced the annual festival Easter at King's, and a series of performances throughout the year, Concerts at King's.
He was influential in the musical world beyond the choir, conducting a number of ensembles including the Academy of Ancient Music and the BBC Singers, and through his association with the Cambridge University Musical Society.
Prior to Sir Stephen's tenure at King's, he held key posts at Westminster Abbey and Westminster Cathedral.
In 2019, he was knighted in the Queen's Birthday Honours for services to choral music.
King's College choir was founded by King Henry VI in 1441 and is regarded as one of the world's finest choral groups.
It comprises the conductor and 16 boy choristers, who are educated on scholarships at King's College School, as well as 14 choral scholars and two organ scholars, who study a variety of subjects in the college.
The choir's Christmas Eve performance was introduced in 1918 and has been broadcast also every year since 1928.