How do you learn to play an instrument? Practice. How do you learn to write serendipitously? Practice. How do you learn chemistry? Practice? What exactly? I am sure you can practice incorrectly. For example, a musician could play out of time. Something a metronome would solve. A musician playing out of time could continue to practice, unaware of their mistakes. The metronome provides immediate feedback to the musician, letting them know if they are out of time or not. This feedback changes the musician’s behavior much like an instructor telling students if they are right or wrong. 

A musician could also practice playing scales. Any music teacher would tell you this is a great thing to practice. Playing scales has an immediate benefit, countless sheets of music a musician could encounter while playing in a symphony would resemble scales. The ability to play scales can transfer to other applications. But how different are the scales in practice compared to the scales embedded within Mozart, Beethoven, or Tchaikovsky? I would say they are incredibly similar, only difference is the notes surrounding that scale, perhaps a musician must move around the fret board in a more specific way, but the scale remains embedded in the task. When do these scales become unrecognizable from their original context? That depends on how many notes differ from the original eight notes a scale makes up. I would say that three notes are required to establish a pattern of tonality. Two notes cannot establish a minor or major scale.

Practice is how people learn.

JLS