Legendary British music producer George Martin, who turned the Beatles into the best-selling band in history, has died at the age of 90, his family said on Wednesday, as tributes poured in.
Beatles drummer Ringo Starr was the first to give the news, writing on Twitter: "God bless George Martin peace and love to Judy and his family... George will be missed," alongside a black-and-white picture of the "Fab Four" with Martin.
Martin's family confirmed that the producer, who helped revolutionise the sound of pop music, died at home on Tuesday, and thanked "everyone for their thoughts, prayers and messages of support".
British Prime Minister David Cameron led praise for the producer, who signed up the young band from Liverpool when he headed the Parlophone label after hearing their demo record in 1962.
"Sir George Martin was a giant of music -- working with the Fab Four to create the world's most enduring pop music," Cameron tweeted.
Martin's innovative recording techniques and role as authoritarian mentor was so essential to the band's success that he was nicknamed the "Fifth Beatle".
"R.I.P. George Martin. I'm so gutted I don't have many words," late band member John Lennon's son Sean wrote on Instagram.
Martin was born on January 3, 1926, a carpenter's son from north London, and learned the piano as a teenager, dreaming of becoming a composer and performer like Sergei Rachmaninov.
After serving in World War II, he studied at the prestigious Guildhall School of Music and began playing the oboe in bars and clubs around London.
His first job was at the BBC's music library.
He then joined the record label Parlophone, a division of EMI, and rose to become its head by 1955 at the age of just 29.
Martin quickly realised the Beatles' potential after first hearing them in 1962.
"I liked them as people apart from anything else and I was convinced that we had the makings of a hit group," he told Melody Maker magazine in an interview.
But he added: "As composers, they didn't rate. They hadn't shown me that they could write anything at all."
The band's first single "Love Me Do", which reached number four in the charts in October 1962, "was pretty poor but it was the best we could do," he said.
That was followed by "Please Please Me", which made number two, and "From Me To You" in April 1963 -- their first chart-topper.
He also composed scores for the Beatles films "A Hard Day's Night" and "Yellow Submarine".
Martin helped combine the sophistication and discipline of his classical background with their raw rock'n'roll attitude, spearheading the new generation of "British Invasion" groups.
From the string octet on "Eleanor Rigby", the layered psychedelia of "Strawberry Fields Forever" to the orchestral section on "A Day In The Life", Martin's arrangements gave colour and shape to the musical ideas of Lennon and Paul McCartney.
Martin described the creative process of "A Day In The Life" during a 2012 interview with the Wall Street Journal.
"Paul suggested an orchestral orgasm, so I scored 24 measures, from the lowest note to the highest. I told the orchestra: 'Make your own way up there. If you're playing the same note as the chap next to you, you're wrong.'"
He was quick to use new technologies, pioneering techniques such as automatic double tracking -- where two copies of the same track are played milliseconds apart to thicken the sound -- and flanging, where one of the two copies is momentarily slowed down to produce a "whooshing" effect.
The band's use of reversed samples and randomly spliced together snippets of recordings helped develop their later psychedelic sound, spawning a whole new genre of pop music.
After the band split, Martin built the Air Studios on the Caribbean island of Montserrat and went on to work with other artists including Bob Dylan, Sting and Elton John.
Martin produced 30 British number one singles, won six Grammys and was knighted by Queen Elizabeth II in 1996.
The Beatles have sold over 1.6 billion records.