Althoughh private performing arts learning (i.e. piano lessons, voice lessons, acting lessons etc.) are a GREAT starting point for learning basic musical skills, they lack a very key cognitive process that is important for brain developent and for preparation for 'the real world'. That is to have the abilities to use those cross-hemisphere/brain cognitive processes in real-time interaction with others doing the same.

Learning to play a piano piece by oneself, where it is all up to you when all the notes are played, is vastly different than learning how to learn what seems to be a simpler musical part (i.e. just a single melody line) and needing to be able to play that part at exatly the same time as the person next to you (or possibly in an echo format back and forth with that person). When you take that to a full band or choir experience where you have to do that with many other musicians and you are doing it over many songs and styles, the cognitive benefits are expanded exponentially.