In one study of a savant pianist, the researcher, who had heard the man play hundreds of songs flawlessly, was dumbstruck when the savant could not re-create an atonal piece even after a practice session with it. “What I heard seemed so unlikely that I felt obliged to check that the keyboard had not somehow slipped into transposing mode,” the researcher recorded. “But he really had made a mistake, and the errors continued.” Patterns and familiar structures were critical to the savant's extraordinary recall ability.
This bit from David Epstein's Range hit a personal note. No, I'm not a savant, but it made me recall the most difficult music I had to memorize for performing on classical guitar — two atonal pieces. Their difficulty lies exactly in what the savant pianist in Epstein's telling encountered — they negated the patterns and familiar structures that were at the foundations of how I play guitar. Take those away and memorizing passages & chord progressions becomes trickier. It took longer than anything I ever learned before.
But that's the beauty of learning newer things, whether it's music or programming languages. They take you out of what professor Erik Dane calls “cognitive entrenchment.” As David Epstein explains,
[Erik Dane's] suggestions for avoiding it are about the polar opposite of the strict version of the ten-thousand-hours school of thought: vary challenges within a domain drastically, and, as a fellow researcher put it, insist on “having one foot outside your world.”