many styles have used hidden sounds and they generally are all described in the drum maps in the blue manuals.

To use them just highlight the note in step edit and scroll the note switch and ok the result. This can be done in composer, pad or sequencer (I can't remember if the 1400 had pad step edit, I think it did). To play them, just play the nearest note on the keyboard and then change it afterwards, or use octave shifts to listen live.