Stacking 3 of the same shields on top of each other and instructing them in sync Context:
I have an audio track separated into individual channels grouped by frequency and speaker location. I need to play all three of these channels simultaneously and perform instructions like play, stop, repeat, skip across all channels to keep them in sync.
This is part of an outdoor installation so the solution must be modular and robust.
If possible, the most elegant solution I could come up with is to use an Arduino Leonardo and stack 3 Adafruit Music Maker Shield on each other.
Reasons why I think it might be technically feasible:
1. Each shield can share communication over I2C

Looking at the VS1053b Datasheet (the IC used in the shield) the chip at max load consumes Maximum 60mA, and typically 37mA. Arduino can drive a max of 500mA so these three shields should consume a small portion of that.
The Arduino will also be powered via 12v power supply.

Details i'm not so clear on:

How will I differentiate between each shield when sending instructions or do I need to even need consider this if I want them to function as one?
The shield actually uses SPI.

So you will need to trace the chip select and make sure that each shield uses a different arduino pin.