I completed the mouth and the MagicHat now can speak.
I had to make some changes to the circuit for reading audio output. The new version includes two resistors and a capacitor to shift up voltage level by 2.5V
Using an headphone, I cut off one of the speakers and added a connector to be connected to the Arduino board
The video shows MagicHat saying its first word. "Hello". Unfortunately audio quality is not that good due to my smartphone limitations, but it gives the idea!
In the video, you can also see all the hardware ready to be installed