"We were performers...in Liverpool, Hamburg and around the dance halls. What we generated was fantastic when we played straight rock, and there was nobody to touch us in Britain. But as soon as we made it, the edges were knocked off. Brian Epstein put us in suits and all that, and we made it very, very big. We sold out. The music was dead before we even went on the theater tour of Britain. We were feeling shit already, because we had to reduce an hour or two hours' play--and which we were glad [to do] in one way--to twenty minutes, and go on and repeat the same twenty minutes every night. The Beatles' music died then, as musicians. That's why we never improved as musicians. We killed ourselves then to make it--and that was the end of it." --Lennon Remembers, December 1970
Despite the current realities of pop stars lip syncing their way through concerts, the Beatles began as a live band and gradually transitioned into being more of a studio band before giving up on touring in 1966. Whereas currently, lip syncing is a device popularly used to disguise poor singers, the issue for the Beatles was their advanced recording techniques and songs which became increasingly difficult to perform live with the technology available at the time. While the Beatles toured for final time after the release of their 1966 LP Revolver, they never performed a single track off the album on any of the tour dates (though they reportedly rehearsed a few and decided against playing them live). The closest they came to this was performing live the Revolver-era single "Paperback Writer."
The Beatles' television shows were a mixed bag in terms of lip syncing vs. live and depended on the show's format (e.g. Ed Sullivan Show - live until the music video promos for were sent to the show beginning in 1966; Top of the Pops - lip synced; Around the Beatles - lip synced to recordings especially made for the program). Interestingly, union rules prevented the Beatles' music videos in some instances from being aired if they featured a lip-synced performance. The Beatles failed the test with the video "Hello Goodbye," obviously lip synced, but succeeded with the promos for "Hey Jude" and "Revolution," featuring a mixture of a live performance and the 45 single, enhanced by the presence of a studio audience and orchestra in the case of "Hey Jude."
A variation on this theme was present in The Beatles in Nederland television special from 1964 (featuring Ringo's temporary replacement Jimmy Nicol on drums). Perhaps for sound reasons, the special was set up such that the Beatles were to lip sync to their records, but the microphones were left on, leaving the Beatles to sing karaoke to their own recordings. It hardly mattered then, when the audience overtook the stage and crowded out the Beatles - the music played on without them.