Our resident Beatles scholar, "victoriaholt," at VH1.com just put this up for us (she's an LA based broadcast-journalist who protects her anonymity), and I thought it would be of interest to the Board:

The Webster's New World Dictionary of Music lists the Beatles as: Although American in
origin, the rhythm and blues-country music mix plied by the quartet had an indefinably
British lilt: square meter, accented primary beats, minimal syncopation, modal harmony,
lowered submediants in major keys, and a preference for plagal cadences and
consecutive triadic progressions, creating at times a curiously hymnal mood. Their lyrics
were distinguished by suggestive allusions, sensous but not flagrantly erotic, anarchistic
but not destructive, cynical but also humane.

victoria's comment: "That's quite a mouthful!"