|Marty Nemko at the piano during a performance of the show, Retard!|
Alas, standard methods of learning piano or guitar not only are extremely unlikely to make that happen but are stressful rather than recreational. After all, it's far from fun to play scales, let alone have to translate, with 100% accuracy, the squiggles on a piece of sheet music into what your fingers need to do, let alone musically, let alone by heart.
My PsychologyToday.com article today presents the method that I used to learn to play by ear. At the risk of sounding hyperbolic, it really is easy, fun, and is your best shot at learning how to play by ear. The article offers both a six-minute video plus text that basically tells you everything you need to know.
I welcome your feedback on whether it works for you.