The composer was 69. From the BBC:

Having started his musical career as a teenage organist at a Presbyterian church in London, he converted to the Russian Orthodox Church in 1977 and once said that “my way towards God has been to write music”.

James Rushton, managing director of Sir John’s publisher Chester Music, described him as “one of the unique and most inspired voices in music of the last 50 years”.

“His large body of work… is one of the most significant contributions to classical music in our times,” he said.

The report goes on to indicate that Sir John may have lost his faith in recent years, after his heart attack. More on this from a 2013 interview with him:

Tavener’s own spiritual journey has been closely linked with the Orthodox faith, ever since he was received into the Russian Orthodox Church in 1977. His relationship with the Church has become somewhat looser in recent years. When I ask his thoughts on the status of the Orthodox faith in the modern world, he expresses both concerns and hope.

“What worries me today are the aspects of Nationalism, prevalent in Orthodox countries. If it can lose this aspect I think it would make a much stronger impact on a world that is dilapidated and that has lost the precious language of ritual, signs and symbolism. If it hangs on to Nationalism it will remain as ineffectual and dilapidated as the secular culture.”

… “Universalist” is a term Tavener often uses to describe the spirituality of his more recent music. He has become increasingly interested in revealing the “basic truth” that religions share. When I ask Tavener to elaborate, with particular reference to The Veil of the Temple, it becomes clear that, even within this culturally diverse framework, both his music and his faith remain grounded in the traditions of the Orthodox Church.

“My seven hour vigil The Veil of the Temple is constructed like an Orthodox vigil, but within that structure it contains aspects of Hinduism, Islam, Buddhism and the primordial religion of the American Indians. It is my dream for this to be performed in a cathedral in Russia, just as it has been performed in Anglican Cathedrals in England. The way forward must now be Universalist, but we must always keep our Orthodox roots.”

Must be, eh? Ah, that’s too bad. The Guardian’s obituary has more on how he moved away from Orthodoxy and towards Universalism, occasioning a split in 2003 from the Orthodox abbess who was his spiritual mother. He and the Prince of Wales shared both a close friendship and a mutual love of Traditionalist metaphysics. He was a marvelous composer. May he find eternal rest in the arms of the one true God.

(Thanks to the reader who shared this news with me.)