Hi Maryland,
I beleive that the DJx has six seconds of sampling memory, I am not sure if that can be used by plugging in an external sound source and recording into the keyboard, or if it is just for internal samples, try it. It is possible that the line in is just for playing back from an external sound source and jammin.
If you have an external cassette deck, then you can just record from the line out or even the headphone socket of your DJX into your cassette's line in.
I don't own a DJX, having recently bought a Cs2X and SW1000xg, but the DJx sound like fun
to me. it takes ages for me to programme beats into my sequencer, does the DJX create them easily?