Voice teachers use a phrase to help their students become more proficient and that is to "put the song into your muscle memory." That means to practice all of technical aspects of learning the music right from the first. In other words, pay attention to vowel placement, breath management, supporting the descending lines, preparing for high notes and shaping the phrases right from the beginning of your learning adventure.
Muscles have memory. Anyone who does sports or dance knows that. It is the same for walking or running, typing, or writing or drawing, playing a musical instrument, or even the most classic example of riding a bicycle. Those muscles that train to do those activities will soon become proficient and retain the memory of doing the necessary moves and have the proper strength and balance for those activities. The person no longer has to actively think to make the muscles work, they just respond and do their jobs. And once the muscles are trained and strengthened to do the activity, like riding a bike, even after a long absence, a person can pick it up and do it again. It is said that you never forget how to ride a bicycle. Though your skill may get a little rusty, the muscles retain the memory of how to do it.
With training the voice, muscle memory plays a huge role. But there are so many factors that seem to sabotage our efforts to be consistent. I am always amazed, for instance, how long it takes to warm up the voice, especially as you age. Not that it cannot be done, just that gravity and the cares of the day and the human condition can combine to thwart your efforts. I am equally amazed at how wonderful it is to come back to a song once learned in days gone by and feel how effortless it feels to sing again. I was reminded of this recently when teaching one of my students. We were reviewing German lieder trying to choose a recital piece. We came across a challenging Schumman song that I was delighted to find I still remembered. Not only were the notes there, but also the words. Muscles also retain memory for forming words, and not just in your native language, as long as you have put in the effort to learn them.
Another thing I was reminded of recently: In the Mormon Tabernacle Choir we have been preparing for a new recording project. The songs are mostly pieces where we provide support and accompaniment to a world -renown baritone. This soloist has requested that we sing some of our own repertoire with him --- only in his key. That means we have lowered many of the songs that we have sung for ages by at least one whole step and sometimes by a third! And because of the way a soloist needs to be heard above the choir, the sopranos have to sing harmony parts sometimes an octave or more down from where they are used to singing. I did not realize how uncomfortable this would be. These are notes that look fine to sing on the page, but somehow feel so awkward when attempted. We are fighting at least two factors here: 1. We have no muscle memory built yet to deal with the new notes and 2. Our muscles remember doing something quite different with this music and they do not like the change!
Muscle memory can protect us from injury. Ball players can relate to this. They train and train to have the skills to ensure that they can react in an instant properly without straining or injuring themselves to make the play. Dancers stretch and train to become strong and limber enough to do all of their intricate and sometimes gravity defying moves. Violinists are like marathon runners. They surely need technical skill but also amazing endurance to play for hours those incredible symphonic masterworks. Vocalists these days are called upon to not only sing, but often to sing, act and dance all at the same time. They had better put muscle memory into their vocal apparatus before they start moving around on the stage or they could seriously jeopardize their performance. Having worked hard to put the right technique into the muscle memory can be a protection from the stress of adding more and more layers to the performance. Building up endurance is essential for the triple threat!
So, in whatever you are doing, especially in singing, take the time and put in the effort to create the proper muscle memory. The worst thing you could do is let your muscles remember singing flat or out of tune or using the wrong support or vowel placement. It is more difficult to overcome bad habits than create good habits from the start. Muscles have memory -- hopefully they will be only good memories!