Muscle memory, also known as motor memory, refers to the process by which your brain and muscles work together to perform a specific action or movement. When you first learn to play an instrument, your brain must consciously process the information and send signals to your muscles to move in a specific way. As you practice and repeat the same movements, your brain develops a "memory" of them, allowing your muscles to perform them more easily and smoothly.
In the context of learning an instrument, muscle memory is crucial for developing the dexterity and proficiency needed to play complex pieces. For example, when you first learn to play a chord on the guitar, you may need to think about each finger placement individually. But as you practice, your fingers will begin to move to the correct positions automatically without you having to think about it. Learning to play a para-diddle on the drum kit at first is hard. Taking the time to learn which hand plays when takes time and repetition. Likewise, when learning a major scale on the piano, knowing the correct order of tones and semitones and how that translates when applying it to white and black notes needs time and consistent practice to allow the notes to flow musically as you play. This is muscle memory at work.
It's important to note that muscle memory is not just about physical movement but also the coordination between the mind and body. It also helps to develop the sensation of touch and pressure and improves the precision and accuracy of your movements.
It is important to note that muscle memory is not permanent. It requires maintenance and repetition, and if you don't practice for an extended period of time, muscle memory will fade. That's why it's important to practice regularly and consistently to maintain muscle memory and build skill proficiency on an instrument.
Whatever instrument you are learning, keep it fun and make it interesting for yourself and remember you will always make mistakes, which is a good thing. It means you are pushing yourself, and soon those mistakes are what will help you become a better player.