For me one feature of 'Avant Garde' is when an artist is trying to expel from himself as close a reproduction of himself as possible, that is, the creation with the least possible artifice or superficiality, with the belief that the more genuine it is the more it will resemble everybody else also - and can therefore be separated from its creator, more so than either those superficially and traditionally ‘representational’ works grounded in previously successful (popular) methods, or other more intentionally 'weird' or wilfully obscure stuff. As such it’s also often linked with an impulse to destroy ‘art’ - both high and low, and as people have always discovered the act of detruction also creates anew. To me the Beatles were too interested in making superficially ‘different’ recordings in order to maintain their success and actually imploded because of their different outlooks on the avant garde.