Research
Here is a brief sample of some research linking music learning to brain development:
https://www.frontiersin.org/articles/10.3389/fpsyg.2019.01704/full
"Converging evidence has demonstrated that musical training is associated with improved perceptual and cognitive skills, including executive functions and general intelligence, particularly in childhood. "
https://nyaspubs.onlinelibrary.wiley.com/doi/full/10.1196/annals.1360.015
"Data from our cross-sectional study of nine- to eleven-year-old children with an average of four years of musical training suggest that the predicted effects become stronger, and that transfer effects begin to emerge in addition to those strong effects in closely related motor and auditory domains."
https://www.jneurosci.org/content/23/27/9240#sec-3
"In comparing these three groups (professional musicians, amateur musicians, and non-musicians)...the gray matter volume is highest in professional musicians, intermediate in amateur musicians, and lowest in non-musicians."
Many further studies can be found easily. View a short list of them here: