Learning to play music is challenging in many ways, including requiring a blend of cognitive decoding, motor coordination, physical memory, and sensory listening.
If you are reading music as you play, that requires you to engage in several different tasks at the same time. Most fundamentally, you have to translate various musical symbols, including, notes, clefs, and key signatures into what you are playing—and do it as you play. You also have to keep the rhythm as you play the notes according to their designated meter. You have to be able to find the notes to play in the appropriate rhythm on your instrument without looking, which becomes second nature as you learn to play more and more complex melodies and harmonies. And you have to control how hard or soft you play, that is, regulate your touch or voice to manage volume and other aspects of expression, like tone quality.
Music also demands a unique blend of motor skills. Most instruments require you to do something different with your left and right hands; that takes time and training to get used to, and each instrument has its own challenges. Playing an instrument well requires a special type of technique that has to be learned, like how you set and move your hands on a piano keyboard. That’s a lifelong effort that becomes increasingly challenging as you play more complex music. It can take thousands of repetitions before hand movements shift from conscious effort to effortless execution.
Perhaps the most challenging aspect of play music is that, unlike writing or speaking, you can’t stop to correct yourself. If you make a mistake, you must instantly adjust your pitch, rhythm, or hand position while keeping up with the tempo. Hearing your mistakes in real time can also create angst and frustration. Still, not matter how accomplished you become, you are going to make mistakes, and smoothing them over so they are unnoticeable, or at least less noticeable, is part of learning to play and perform music well.