Who was the 'fifth Beatle'?

There is a long list of possible candidates, with Brian Epstein a very strong contender. Pete Best also has a claim, as a he was a full band member until August 1962. Musically, however, there is a clear winner and that is the man who offered them their first recording contract and guided them to new frontiers in pop music.

When The Beatles entered Abbey Road as very raw musicians without any formal training. They were good live performers but had no experience of working in a studio. None could read music and only Paul had a natural facility for explaining musical ideas in a form that technically trained musicians could follow. 

Their early compositions had potential but they needed Martin's experience to make them commercial. PLEASE PLEASE ME for example, was initially a Roy Orbison derivative dirge until Martin inspired Lennon to liven it up. The result was The Beatles first number one single.

What did George Martin contribute musically?

For five years the partnership blossomed, helped by the practical audio engineering genius of Geoff Emerick. The Beatles were very fast learners and with each album they set  new challenges which Martin heroically rose to. 

The death of Brian Epstein in August 1967 marked the end of this golden era.  The next project - the ill-fated TV special Magical Mystery Tour - was panned by the critics. Resentment grew against Paul and this merged with another gripe - that George Martin had been taking too much credit. By the White Album Martin was increasingly pushed to the sidelines. Geoff Emerick resigned and Martin was not retained for the recording of Let it Be. 

Unleashed from Martin, and under the direction of Phil Spector, the Let it Be recording sessions produced a sonic mess. While this was being resolved in post-production The Beatles were at the point of collapse, with personal relations between Paul and the others extremely poor. 

Martin returns

Ironically, the one thing The Beatles did agree about was that they deserved a better swansong. Paul proposed bringing back Martin and Emerick for one last album. To his surprise the others agreed.

The Abbey Road sessions went remarkably smoothly, despite the increasing rancour of their personal and legal disputes. The result was a magnificent album that stands with their finest achivements.