Better start with music playgroup b4 learning musical instruments to arouse our children's interests and train up the rhythms. I see many young kids start learning Piano class and give up later as they're too small to persist the 'interests' & found boring for 1-1 teaching.
For me, I'm waiting the day that my son asked me to let him learn the musical instrument. But I'd create muscial environment to him with an aim to 'strengthen' his interest.