As I child I used to hate when my teacher asked me to relearn pieces I had played before. One teacher tried to persuade me, “Relearning a piece is like visiting an old friend,” an analogy that meant little to 13-year-old me.
Nowadays I’m so inundated with new music that I’m usually relieved when I don’t need to learn a piece from scratch. Although in a few cases I’ve thought relearning a piece was more like visiting an old enemy than an old friend, I have a few tips to ease the process for friends and enemies alike.
Relearn it while you sleep. I swear by this trick, but it still amazes me every time. The first day, I’ll play the entire piece once through without stopping, mistakes and all. After a night’s sleep, my brain seems to retrieve the music from long-term storage. The next day my memory of the piece is magically improved, and I continue practicing from there.
You can read more about the phenomenon of learning while sleeping over at Bulletproof Musician.
Fingerings: take them or leave them. Sometimes I kick myself for not writing down the fingering I used previously. Sometimes I try my old fingering and think, “Who came up with this shitty fingering?” In the past I’ve wasted time trying to master a previous fingering, thinking that if it worked for me before, it must work again. Now I just give fingerings a try or two and come up with a new one if they don’t work.
Don’t begin at the beginning. Instead of relearning the piece from beginning to end, I start with the most difficult passages. If nothing stands out as being particularly troublesome, I work from the end to the beginning, since most likely I learned it the other way around the first time.
How do you feel about relearning old pieces? Do you have any tips or tricks?

I’m singing it like this, which is not 100% accurate, and watching JO.