If, and when, authorized by the Department of Public Instruction of this Commonwealth, public concerts may be rendered and broadcast anywhere within this Commonwealth on Sunday after twelve o'clock noon; and it shall be lawful for the person or persons rendering any such concert to charge an admission fee thereto at a rate which it is estimated will cover the expenses of rendering such concert, including light, heat and compensation to ushers, janitors and musicians: Provided, That the cost of light and heat and compensation to ushers, janitors and musicians shall not exceed an amount computed at the rate charged for light and heat and compensation to ushers, janitors and musicians for week-days: And provided further, That should the amount collected for admission fees to any such concert exceed the actual expenses for light, heat and compensation to ushers, janitors and musicians, the excess shall be paid to the Department of Public Instruction of this Commonwealth to be employed by it for such public music purposes as it may deem proper.