"It is with profound sorrow and sadness that Cherry Red Records and Esoteric Recordings regret to announce that Ray Thomas, founder member, flautist and vocalist of the Moody Blues, passed away suddenly at his home in Surrey on Thursday 4th January 2018," the record label said in a statement.
"We are deeply shocked by his passing and will miss his warmth, humour and kindness. It was a privilege to have known and worked with him and our thoughts are with his family and his wife Lee at this sad time."
The singer, songwriter and musician was one of the founding members of The Moody Blues, and remained with them until 2002 when he retired due to ill health.
In 2014 Ray confirmed that he'd been diagnosed with prostate cancer, but assured fans it was largely treatable.
In a statement he said: “My cancer was in-operable but I have a fantastic doctor who immediately started me on a new treatment that has had 90 per cent success rate.
"The cancer is being held in remission but I'll be receiving this treatment for the rest of my life. I have four close friends who have all endured some kind of surgery or treatment for this cancer and all are doing well.
Ray and his bandmates are due to be inducted into the Rock & Roll Hall of Fame later this year.
His seven albums with the band sold over 70 million copies and included hit singles Nights in White Satin and Go Now.
Born in Stourport-on-Severn on 29th December 1941, Ray was a member of various Birmingham Blues and Soul groups in the early 1960s, notably with El Riot and the Rebels, who also featured John Lodge and Mike Pinder at various stages in their existence. Ray formed The Krew Cats with Mike Pinder in 1963 and the group performed on the Hamburg club scene that year. Returning to Birmingham, Thomas and Pinder formed the Moody Blues with Denny Laine, Graeme Edge and Clint Warwick. The band signed to Decca Records and enjoyed a worldwide hit with their cover of Bessie Banks’ “Go Now” in January 1965.
In October 1966 the Moody Blues line-up changed with the recruitment of Justin Hayward and John Lodge to replace the departing Denny Laine and Clint Warwick. The musical style of the group changed dramatically with the incorporation of the Mellotron into their sound, along with Ray’s evocative flute playing.
The band’s 1967 single “Nights in White Satin” (from the ground breaking album “Days of Future Passed” - a number one album in the USA in 1972) was graced by a magical flute solo from Ray, contributing to the evocative arrangement of the song. Over seven albums released between 1967 and 1972 the Moody Blues enjoyed major success, and each album was graced with compositions by Ray such as “Legend of a Mind” (about the psychedelic champion Timothy Leary), “Eternity Road”, “And the Tide Rushes In” and “For My Lady”.
In the mid 1970s Ray recorded two successful solo albums; “From Mighty Oaks” (1975) and “Hopes Wishes and Dreams” (1976). The Moody Blues success continued into the 1980s. Ray’s song “Veteran Cosmic Rocker” (from 1981’s “Long Distance Voyager”) highlighted Ray’s marvellous sense of humour.