Connect the audio output jack (such as the headphone jack or line out jack) of your computer or mobile device to the MIX IN jack on the TD-1KPX's sound module using an audio cable. Both sounds will play through the headphones connected to the sound module.
Use an audio cable with a stereo mini plug on the sound module end, and a plug matching the connected device's jack on the other end. The cable must not contain a built-in resistor.
Adjust the volume of the external audio on the connected device.