Audio via 'tone' on headphone jack is too loud

[Cthulahoop]

Using tone function to play sound over the headphone jack is too loud for comfort. While the design has specified a resistor for the headphone jack circuit, it would be better to have a small potentiometer or find a way to limit the volume via code.

[Cthulahoop]

Depending on what you have plugged into the headphone jack this varies wildly. That said, the tone library is certainly capable of making uncomfortably loud noises over speakers and I'd avoid sending tones to a powered device in most circumstances.
Workaround: I recommend adding a 10k potentiometer on the headphone jack circuit in line with the resistor. This allows for the most flexibility.