There's an article in the March 2008 issue of Scientific American called "White Matter Matters", which talks about the role of "white matter", or the axons that connect neurons in different parts of the brain, together with the myelin sheath that acts as a sort of insulation for them. Apparently, when the myelin sheath is thicker and has fewer gaps, the nerve impulses travel a lot faster.
But here's the interesting part. "Piano virtuoso Fredrik Ullén... also happens to be an associate professor at the Stockholm Brain Institute in Sweden.... Ullén found that in professional pianists, certain white matter regions are more highly developed than in nonmusicians. These regions connect parts of the cerebral cortex that are crucial to coordinated movement of the fingers with areas involving other cognitive processes that operate when making music.
"He also found that the more hours a day a musician had practiced over time the stronger the [characteristic] signals were in these white matter tracts; the axons were more heavily myelinated or tightly packed...
"...Ullén's studies of accomplished pianists revealed an additional finding: white matter was more highly developed throughout the brains of individuals who had taken up the instrument at an early age. In people who learned after adolescence, white matter development was increased only in the forebrain -- the region that was still undergoing myelination.
"This finding suggests that the insulating of nerve fibers in part determines age limits for learning new skills -- windows of opportunity, or critical periods, when certain learning can occur, or at least occur readily."
In other words, the earlier you start, and the more time you spend practicing, the better chance you have of being an "accomplished player". It has to do with your brain, not your muscles.
Comments?
EDIT: Here's Ullén's personal website. He seems to have recorded a LOT of Sorabji...
https://www.fredrikullen.com/