How long does it take a pianist to retrain muscle memory to play a new motion?

This is a wonderful question. There is no such thing, literally, as muscle memory. Movement is hardwired into the brain, not the muscles.

New muscle memory movement is very easy to wire into the brain and it can be immediate however, the brain never forgets the old patterns so, as a musician, if you get nervous or your body is cold, or you go into autopilot, it is very easy for the old movements to reassert themselves and take over despite new and more efficient neural pathways having been created since. This is especially true for musicians and also, how and what we play is very important.  This is why musicians often claim they can play perfectly in their living room but on stage it all falls apart. What is happening is the old muscle memory takes over because of environmental factors such as the presence of an audience, different bench height, temperature, nerves, etcetera. 

There is another danger here. Many teachers instruct the student to build strength and endurance to overcome technical deficiencies. This works to a certain extent but also puts the musician on the path to injury. If the musician then learns new and proper movements, the improper muscles used previously will immediately atrophy. This is why improperly trained musicians feel rusty or stiff after missing a few days of practice because the wrongly built muscles will get weak, quickly. Proper playing utilizes fulcrums, alignment, gravity, ergonomics and the laws of physics, not muscle. This is counter intuitive to most musicians and to many teachers who are ignorant of anatomy and physics. Mediocrity is the result of using the wrong muscles, not lack of talent. This is because most teachers have no idea what they are doing. They only know what they know but what they don’t know is what creates injury, tension, fatigue and sloppy playing.

A beginning student may learn a piece of music and there may be flaws in his movement. Over time he gets better and learns new songs and rewires some of the improper movements in his brain. He progresses further and his technique improves and his brain learns newer and even more proper movement. THE DANGER is playing old repertoire because even though his technique improves and he now has proper movements, the brain remembers the lesser or improper movements of previous repertoire from a time when he moved less properly. It is important for musicians to either never play old repertoire or, re-learn each piece with the newer, more proper motions.

The greatest danger is, as I previously said, the improper muscles atrophy if not used. If a musician built improper muscles to play a piece well, then as he progresses and loses that muscle because it is no longer needed since he is more ergonomic now, then he plays that old repertoire, the brain expects that the former muscle is there and tries to play the work “normally.” Since the muscle is no longer present, this is when the musician runs the risk of greatly injuring themselves. This is why a well trained musician can one day, out of nowhere, injure themselves.  Most injuries are actually cumulative and it is one of those "muscle memory" moments that serves as the proverbial "straw that breaks the camel's back."

In addition, rewiring your brain on your instrument isn’t sufficient. You must simultaneously do the same with how you ring a doorbell, tie your shoes, brush your teeth, pick up a piece of paper, type, swipe, wipe . . .

There is no such thing as repetitive strain, only improper movement.  If you move improperly, all movement can become repetitive strain and as I said, it is cumulative.  That is why a forty year old might get out of bed with stiffness, aches and pains while a 70 who has moved properly all their lives can rise with elan and alacrity.  You can take that to the movement bank.

Owning our Mistakes, Honoring our Mistakes, Everybody Makes

I recently performed a concert with a young artist who is going off to college to study opera.  He has dreams to then move to Europe to live and perform music.  Not only does this young man have a deep and rich bass voice but, he was also a pleasure to accompany.  Rarely do I get to play for someone who can both lead and follow an accompanist at the same time.  Many singers will either hijack a piece and force the accompanist to blatantly follow them or in contrast slavishly follow the accompanist.  When I encounter a singer who is neither a leader nor follower but does both, that is when music happens and a pleasure to work with. 

There was one moment however when he began to sing the wrong verse at the end of the song.  He stopped and corrected himself, everyone knew he made a mistake.  Many musicians learn and memorize their music from rote by practicing them dozens of times over until it is "memorized."  That method can set up many traps and things to go wrong without notice.  Rare is the musician who eats, drinks and sleeps their craft so that they are one with the song. 

I once played the show "Nunsense" for a year and a half, performing six shows per week.  All the musicians in the pit had the score memorized.  One evening, Mother Superior accidentally sang the wrong lyrics and without a second thought, all the musicians looked at one another and we all seamlessly jumped to the spot where she was.  After her verse was over, knowing that she skipped an important lyric, Mother Superior walked to the edge of the stage, looked down and said to the pit "Vamp boys."  Then she proceeded to tell the audience that she skipped a verse and said to the pit "take it back to the second verse" and we all flipped our pages, she counted us off and it was magic to have a mistake a living and breathing part of the performance.   

At my concert last weekend when my bass started to sing the wrong lyric and melody, I knew exactly where he was and was prepared to jump to that spot because I was prepared for the possibilities.  When I practice music, I jump around on the pages, mixing and matching beginnings and endings, playing the piece in different keys, different styles and in general, exploring the possibilities of the work.  This helps me to learn it and to be prepared for whatever may go wrong or, in other words - own the song.  I thrive on these challenges.

My suggestion for all musicians, especially singers, when you practice with your accompanist, don't just practice the song the way it is "supposed to go."  Play with it.  Try different rhythms, accents and styles.  Without notice, jump to a different section so that the accompanist has to find you.  If your accompanist can't do this, find a new accompanist.  There is nothing more frustrating than trying to make music with someone who is not a "musician."  Music should not be something which is regurgitated from a page or set in stone.  It should be a living breathing expression of our selves and spirit.

The worse thing for a musician to do when they encounter a bump in the road is to stop.  Don't train your mind to stop.  Don't practice making mistakes.  Train your mind to be flexible and prepared for the possibilities.  I once worked with a great singer who during rehearsals would stop every time she made a mistake.  That practice manifested itself when she made a mistake on stage, she didn't know how to recover and everyone in the audience knew it.  It also made rehearsals unbearable for me.

If one were to tell the story of Goldilocks and the Three Bears, chances are we are not reciting a memorized version of the story but, extemporizing, improvising and re-living the story pretty much in our own words.  If we make a mistake, we don't stop, go back or apologize.  We effortlessly and almost invisibly correct it on the fly and continue with the story.  Nobody would even notice.  Music can be like that too if we are not a slave to notation, propriety or our egos.  The purpose of telling the story is to tell the story.  The purpose of music should be to tell a story, not put on a concert.  Janis Joplin once said that she doesn't put on concerts when she sings, she makes love to the audience. 

This is what making music should be about. That is the difference between an amateur, professional and artist.  Very often amateurs can also be artists and very often, professionals can be mere amateurs.