foxonix created the topic: Why is the audio sped up when I use the Arduino Shield?
The clock speed (and therefore the audio playback speed) is controlled by 180k resistor Rosc. The Arduino Shield has this resistor installed, and stock Project Boards also have this resistor installed. If your Project Board is plugged into the Arduino shield and the audio playback is sped up, remove the resistor on the Project Board. This will return the audio playback speed to normal.