UPDATED with Paul McCartney tribute and more details throughout: George Martin, a semi-retired producer of classical music recordings until he became “the Fifth Beatle” as producer on all of the legendary group’s studio albums and films during a career that spanned six decades, has died. He was 90. Ringo Starr confirmed Martin’s death in a tweet tonight but offered no details:

Martin’s classical training had a profound impact on shaping the Beatles’ recordings as they emerged in the early 1960s from a nightclub skiffle band covering American rock to an art-song band whose music was created as much in the studio as in performance. Martin built orchestral arrangements to back the increasingly complex works by John Lennon and Paul McCartney and added his own filigree to the music, as in the quasi-Baroque piano riff on “In My Life.” Martin also worked on the soundtracks the Beatles’ movies (A Hard Days’ Night, Help, Yellow Submarine)  and with the individual band members after the band’s 1970 breakup. Martin won two Ivor Novello awards and six Grammys throughout his career.

McCartney, one of the two surviving Beatles, released this tribute:

“If anyone earned the title of the fifth Beatle it was George. From the day that he gave The Beatles our first recording contract, to the last time I saw him, he was the most generous, intelligent and musical person I’ve ever had the pleasure to know. It’s hard to choose favourite memories of my time with George, there are so many but one that comes to mind was the time I brought the song ‘Yesterday’ to a recording session and the guys in the band suggested that I sang it solo and accompany myself on guitar. After I had done this George Martin said to me, ‘Paul I have an idea of putting a string quartet on the record.’ I said, ‘Oh no George, we are a rock and roll band and I don’t think it’s a good idea.’

“With the gentle bedside manner of a great producer he said to me, ‘Let us try it and if it doesn’t work we won’t use it and we’ll go with your solo version.’ I agreed to this and went round to his house the next day to work on the arrangement. He took my chords that I showed him and spread the notes out across the piano, putting the cello in the low octave and the first violin in a high octave and gave me my first lesson in how strings were voiced for a quartet.

“When we recorded the string quartet at Abbey Road, it was so thrilling to know his idea was so correct that I went round telling people about it for weeks. His idea obviously worked because the song subsequently became one of the most recorded songs ever with versions by Frank Sinatra, Elvis Presley, Ray Charles, Marvin Gaye and thousands more. This is just one of the many memories I have of George who went on to help me with arrangements on ‘Eleanor Rigby’, ‘Live and Let Die’ and many other songs of mine…The world has lost a truly great man who left an indelible mark on my soul and the history of British music. God bless you George and all who sail in you!”

Among the many other acts he produced were Jeff Beck, Elton John, Ella Fitzgerald, Gerry and The Pacemakers, America, Jimmy Webb, Kenny Rogers, Cheap Trick, UFO and Celine Dion. Years after John Lennon, Paul McCartney, George Harrison and Ringo Starr had stopped recording as a band, Martin was a driving force behind Beatles Love, the popular Cirque du Soleil show that has been a Las Vegas mainstay for a decade.

The list of Beatles’ masterpieces  to which he contributed — songs not only great in their own way but in their influence on rock music across the board — is as impressive as it is extensive, from No. 1 Beatles hits ranging from “She Loves You” and “I Want to Hold Your Hand” to the classical Indian influences that suffused Harrison’s contributions in Rubber Soul, to the psychedelia of “A Day in the Life,” “Come Together” and “Let It Be.” Martin’s 1992 documentary about the producing of Sergeant Pepper’s Lonely Hearts Club Band, produced by London Weekend Television for The Southbank Show, is a classic, and it’s widely available.

Martin also produced a slew of chart-topping singles for other acts on both sides of the pond, starting with the Temperance Seven’s “You’re Driving Me Crazy” in 1961 and including Billy J. Kramer and the Dakotas’ “Bad to Me” and America’s “Sister Golden Hair.” In the early 1980s, he would produce mega-hit duets featuring Paul McCartney and two Motown legends: “Ebony and Ivory” with Stevie Wonder and “Say Say Say” with Michael Jackson. In 1997, Martin produced Sir Elton’s remake of “Candle in the Wind” as a tribute to Princess Diana in the wake of her death in a Paris car crash. It became one of the best-selling singles of all time.

Martin also was active in non-Beatles films, producing McCartney & Wings’ “Live and Let Die,” a Best Song Oscar nominee, and composing the original score for that 1973 James Bond movie. He produced Shirley Bassey’s classic Bond track “Goldfinger” and years earlier the Oscar-nominated “Alfie,” written by Burt Bacharach and Hal David and performed by Cilia Black.

But Martin always will be most closely associated with the world’s most popular band. Born on January 3, 1926, in London, he met the Beatles in 1962 after his career as a classical music producer essentially had been sidelined. He signed the boys from Liverpool to their first record deal at his Parlophone label, after others turned them down. Martin would continue to work with the band through all of its studio albums and oversaw postproduction on the Beatles Anthology compilations in the 1990s. In 2006, he and his son Giles Martin remixed dozens of classic tracks for the Love show, whose premiere he attended in 2006.

Sir George was knighted in 1996, a year ahead of McCartney.