are you allowed to start getting music lessons which he has not had beforehand during sefirah?
Rav Heinemann told us:
If you are practicing for your parnasa or are practicing because you want to have the choice to enter such a field, then that would be the equivalent of practicing accounting when you’re unsure if you want to be an accountant. The Shulchan Aruch (560:3) says you cannot listen to music “לְשַׂמֵּחַ בָּהֶם’, but to learn a profession isn’t a form a שמחה.
It would seem if you are would like to have the potential to enter the field of music for a job and would therefore require getting music lessons, you could start during sefira - just as it would be permitted to begin studying for accounting or dental school during the sefira.