Yes ! The CDP-230 has a 3.5 mm (1/8 inch) TRS "Audio In" mini-stereo jack on the rear panel for the connection of MP3 players, CD players*, cassette tape players* etc to provide for playing along with backing tracks. However, it does not have a "Center Channel Cancel" feature for removing the center channel (usually the singer) of a stereo performance signal applied to this jack, and you have to control the volume balance between the CDP-230's output and the connected device's output with the volume control on the connected device, as the CDP-230 has no provision for controlling this balance with its own internal circuitry.
* Consult the nearest Merriam-Webster dictionary for complete explanations of what these devices are (were).
If you would like a manual for more info on the CDP-230, you can download a PDF copy for free from here:
http://support.casio.com/en/manual/manualfile.php?cid=008006005
This is an official Casio site, so it is a safe download site. Page EN-6 shows the rear panel connections and Page EN-68 describes the "Audio In" connection.
