The Beatles were the most popular and influential rock act of all time, but their significance cannot solely be measured in sales records (as impressive as those are). They synthesized all that was good about early rock and roll, and changed it into something original and even more exciting. They established the prototype for the self-contained rock group that wrote and performed their own material. As composers, their craft and melodic inventiveness were second to none, and key to the evolution of rock from its blues/R&B-based forms into a style that was far more eclectic, but equally visceral. As singers, both John Lennon and Paul McCartney were among the best and most expressive vocalists in rock; the group's harmonies were intricate and exhilarating. As performers, they were (at least until touring had ground them down) exciting and photogenic; when they retreated into the studio, they were instrumental in pioneering advanced techniques and multi-layered arrangements. They were also the first British rock group to achieve worldwide prominence, launching a British Invasion that made rock truly an international phenomenon. Guitarist and teenage rebel John Lennon got hooked on rock 'n' roll in the mid-1950s, and formed a band, the Quarrymen, at his Liverpool high school. Around mid-1957, the Quarrymen were joined by another guitarist, Paul McCartney, nearly two years Lennon's junior. A bit later they were joined by another guitarist, George Harrison, a friend of McCartney's. The Quarrymen would change lineups constantly in the late 1950s, eventually reducing to the core trio of guitarists.

The British Invasion occurred in the mid-'60s, when a wave of English rock & roll bands crossed over into the American market after the breakthrough success of the Beatles. Though not all of the bands sounded similar -- they ranged from the hard rock of the Rollings Stones and Kinks to the sweet pop of Gerry & the Pacemakers and Herman's Hermits -- each group was heavily influenced by American rock & roll, blues, and R&B. British Invasion bands were either blues-based rockers or pop/rockers with ringing guitars and catchy hooks and melodies. Between 1964 and 1966, the British bands dominated the American charts, as well as the charts in the UK. In that time, there was a second wave of British Invasion bands -- such as the Who and the Zombies -- which were indebted to both American rock and British Invasion pop. By the late '60s, many of the bands had become rock icons but a greater number didn't survive the transition into the post-=Sgt. Pepper= era.

Merseybeat was the original sound of the British Invasion -- a driving, melodic sound that was hybrid of American rock & roll and R&B and British skiffle. The Beatles' early records, like "Please Please Me" and "Love Me Do," were the prototypes of the genre, and soon other Liverpudlian bands like Gerry & the Pacemakers, Billy J. Kramer and the Searchers were following the same style. The sound was called Merseybeat because of the Mersey river in Liverpool. Merseybeat flourished throughout 1963 and the first half of 1964. Shortly afterward, R&B-oriented bands like the Rolling Stones, the Kinks, the Yardbirds appeared, as did pop groups like the Hollies and Freddie & the Dreamers. While these pop groups were influenced by Merseybeat the style itself was losing ground, especially since the Beatles had begun to expand their stylistic reach.