Ultimately, every aspect of an aspiring musician's performance must become automatic, achieved with as little effort as possible, like the process of an experienced driver coordinating the steering wheel and the brakes in turning the corner. The same happens with music; initially, each element takes intense concentration.
Yet another challenge stems from the fact that the brain is ordinarily bound by what is known as the speed-accuracy trade-off: for virtually anything we do, the faster we go, the more likely we are to make errors. Haste really does tend to make waste. In order to be effective, musicians must circunvent this law, playing both quickly and accurately.
Alas, the only known way to defy the speed-accuracy trade-off is through practice, using the only technique that the brain can bring to bear, a process known as automatization or proceduralization, in which in which the brain makes a transition from explicit or "declarative" knowledge, which can in principle be verbally articulated (albeit slowly), to implicit or "procedural" knowledge, which can be executed rapidly. As knowledge becomes proceduralized, we sometimes feel as if we know something in our fingers or muscles but lose the capacity to explicitly explain what is going on.
During this process, simple steps get combined or "chunked" into more efficient, larger units. (…) (E)ventually, some of the skills that initially required a great deal of effort become so automatic they take less conscious focus and leave room for other tasks.
Deliberate practice can presumably make this happen faster, by ensuring that what gets proceduralized is the right sets of habits. When practice regimes aren't selected with care, the learner may wind up automatizing bad habits and thus enshrine sloppy and inadequate procedures, in a way that impedes future progress.
At the neural level, proceduralization consists of a wide array of carefully coordinated processes, including changes to both gray matter (neural cell bodies) and white matter (axons and dendrites that connect between neurons). Existing neural connections (synapses) must be made more efficient, new dendritic spines may be formed, and proteins must be synthesized. Often, mental representations that are initially stored in the prefrontal cortex (which we associate with conscious cognition) shift tones parts of the brain such as the hippocampus, associated with memory, and the motor cortex and the basal ganglia, which are in charge of the more immediate control of our muscles.
Until all that practice-spurred brain growth starts to happen, you might be able to enjoy music, but you certainly won't be able to play it.
Guitar Zero. The New Musician and the Science of Learning (páginas 51-52).