542. It is permissible for adults as well as children to learn the art of halal music in music schools or other places as long as their visits to such places do not have any negative effect on their proper upbringing.
https://www.al-islam.org/a-code-of-practice-for-muslims-in-the-west-ayatullah-sistani/music-singing-dancing
567. Question: Musical instruments are of different kinds. Sometimes they are used in musical gatherings and sometimes for soothing the soul. Is it then permissible to buy these instruments, manufacture them, deal in them, or play them to soothe the soul or listen to the ir sounds when someone else is playing them?
Answer: It is not permissible to deal in the instruments of haram entertainment: neither selling nor buying, just as it is not permissible to manufacture them and accept remuneration for making them.
“An instrument of haram entertainment” means that its physical shape—that gives its value and eventually the purpose for acquiring it— is not suitable except for use in haram entertainment.