We decided to add audio to our Christmas display. We already had the PA speakers that we used for out thunder effect on out Halloween Build, so why not repurpose them?
We installed one speaker pointing to the street on the south , and one speaker pointing to the street on the west. Keeping the speakers under the patio sheltered them from the worst of the elements.
We want to keep the sound loud enough that passers-by would hear it, but soft enough so that we didn't hear it in the house (or the neighbors). The speakers are powered, so we left them on and plugged them into our smart outlets so they would come on with the rest of the display.
We kept the mixer and an old iPhone inside the house, leaving only two speaker cables that need to be fed from inside the house to outside. We had the iPhone looping a Christmas playlist, 24/7, but the sound was only "on" when the speakers were powered up with the lights.
So while the music was always playing 24/7 on the iPhone, it was only heard when we powered up the display (which we do through HomeKit automations), which applies power to the speakers when the lights come on.