Most of us agree that the Beatles made great music. But some people don’t believe the Beatles to have been especially good musicians. Quincy Jones famously called them “the worst musicians in the world.” He’s exaggerating, but he has a point. By modern standards, the playing on Beatles records is sloppy. The parts are interesting by the standards of 60s rock, but not nothing that would challenge a jazz or classical player. John, Paul, George and Ringo are pretty good singers and instrumentalists, but you could walk into any music school and quickly find yourself dozens of better ones.
The thing is: I do think the Beatles are great musicians. However, it is not because of their playing, or their singing, or even their songwriting. The Beatles are great because of their ability to create studio recordings. Their albums from Revolver onwards are hugely greater than the sum of the material, arrangements, and performances. Those late albums are masterpieces of recording, editing, mixing, and effects, of hyperrealist timbral and spatial manipulation, and of surrealist tape editing.