I still find it astonishing that in only 6.5 years, their music evolved from Please Please Me to Abbey Road. Only six and a half years, a veritable blink of an eye. And what’s equally remarkable is that in that same scant time they recorded 13 original albums (OK, maybe 12.5 if you deduct the George Martin instrumental content of Yellow Submarine), plus several massive singles that were never on those albums. That pace must have been grueling, both in terms of meeting contractual obligations, and in just being the outlets for their own rapidly changing artistic expression. It’s a wonder they didn’t implode before they did.