You can play .mp3 files with just a Feather M4 plus an amplifier and speaker. However, for the puppet sound playback, we'll make a nice, compact player with some extra features.
The Propmaker FeatherWing gives us a very convenient built-in amplifier and speaker output port, as well as an accelerometer with tap-detection we will use to trigger the sample playback.
With a small battery, USB port extender, and toggle switch for powering the board on and off via the Enable pin, we'll have a great little player that can be embedded inside the puppet, while still allowing it to be triggered from the outside, recharged and even coded without requiring disassembly.
Add Header Pins
Solder a set of female and male header pins to the Feather and FeatherWing respectively as shown here.
This guide shows how to solder in the headers.
The Enable pin on the Feather can be used to turn the board on and off.
Push the wires through the Propmaker FeatherWing's hold as shown (for strain relief) and then solder it to the G and En pads (either wire in either hole is fine).
Connect the battery to the JST battery jack and add a little piece of double-stick foam tape to keep it secure between the two boards.
Fasten with Hardware
Use four M2.5 standoffs and eight short M2.5 screws to fasten the boards together.