Former Beatles drummer Ringo Starr has announced the death of the so-called "fifth Beatle," producer Sir George Martin, at age 90.
Starr posted the news on Twitter Wednesday, with a photograph of Martin with the Beatles captioned "Thank you for all your love and kindness George."
Universal Music Group has confirmed the death, but details have not been released.
British Prime Minister David Cameron tweeted a tribute early Wednesday, calling Martin "a giant of music."
Martin, a classically trained musician, signed the four young Beatles to a music contract in 1962. He was considered essential to their success, helping them arrange, and produce many of their biggest hits, starting with one of their first: 1962's "Love Me Do."
In some cases, Martin's classical music training filled in gaps for band members John Lennon, Paul McCartney, George Harrison, and Starr, who entered the industry with only a basic knowledge of reading and writing music. Martin is credited with scoring now-iconic trumpet solos, string quartet interludes, and piano breaks in some of the Beatles' most memorable songs.
After the breakup of the Beatles in 1970, Martin went on to work with other artists such as Elton John, Bob Dylan, and Sting. He was knighted by the British monarchy in 1996.
Martin continued working on Beatles-related projects, recording two solo albums for Paul McCartney and, in 2006, developing a Beatles-based Cirque de Soleil show called "Love" that has won two Grammy awards for its soundtrack.
Guinness World Records has named Martin as the most successful music producer ever, with more than 50 number-one hit records in Britain and the United States alone, over a career that lasted six decades.