What types of licensing would I need to edit/alter copyright protected music and sell to others?

I would like to start a business offering music editing services to be used by customers however they choose but specifically dance teachers/choreographers to use in competitions and public performances. If I legally purchase or already own the music which I would edit and then sell to the customer, would I still be in violation of intellectual property copyright laws because of redistribution? What if I am only selling the "service" of music editing by editing a copy which the customer already owns? If the songs have been edited are they still protected as a derivative work? Should I be concerned if the customer may be in violation by "playing or performing the material in public" by choreographing a dance to the music? A lot of Qs I know. Just trying to understand this from all angles. Thanks for any advice!