With every single LP, the Beatles shed some creative skin. Decades later, it's still difficult to process their two-year leap from Revolver to Sgt. Pepper's to the White Album. The members also continuously expanded their own roles in the band: It's surprising how many classic Beatles songs feature Paul McCartney behind the drum kit, or John Lennon on lead guitar.  

These small details are crucial in the Beatles' evolution: McCartney's one-man-band performance on White Album gem "Martha My Dear"; Lennon experimenting with an obscure keyboard, the Mellotron, on psychedelic daydream "Strawberry Fields Forever." (Without his introduction of that crucial instrument, who's to say King Crimson would have cemented the prog-rock movement on In the Court of the Crimson King?)

To honor the Fab Four's enduring free spirit, let's look back at 10 of the band's most intriguing instrumental switch-ups.