The MIX IN on the TD-4KP module can be used to connect an external CD player, mp3 player, or cell phone if you have music stored on it. Once connected you can play the TD-4KP's sounds along with the songs in the external player.
1. With a stereo 1/8" - 1/8" cable, connect one end to your external device's headphone output (mp3 player / phone etc.)
2. Connect the opposite end to the MIX IN input on the side panel TD-4.
Increase the headphone volume level on the player, and then play the song.
Turn the VOLUME knob on the TD-4 module to adjust the volume level as desired.