Audio AC coupling capacitors

Ceramic capacitors can be microphonic and might introduce distortion, mylar or polycarbonate would be better.

When you are using capacitors to couple a circuit you need to be worrying about the low frequencies. A coupling capacitor is by definition a high pass circuit.

The larger the capacitor value you chose, the lower your cut off frequency will be on the high pass circuit. Wikipedia shows an example circuit as well as how to pick your capacitor value in respect to your desired cut off frequency and resistance.

As for the type of capacitor, since audio is AC you will need to have a non-polarized capacitor. In my experience, I have never found anything better then a ceramic capacitor for this application.