The RP-401R has a mode called "split mode", which allows you have one tone in your left hand and a different tone in your right hand. You can also specify where you want the split point to be on the piano.
Use this procedure to use and edit split mode:
1) Turn the Split mode feature on by pressing the [Split] button so it's lit.
2) To select the split point, hold down the [Split] button and press the piano key where you want the piano to change tones.
3) To change the tone of the right hand, simply select a tone like you normally would. Select the category of tones you want to choose from first (piano or other), and then use the [+] and [-] buttons to select the specific tone you want to use.
4) To change the tone in the left hand, hold down the [Split] button, and then select a tone as described in step 3. Be aware that you must hold the [Split] button the entire time you are searching and selecting a tone for the left hand. Once you have found the tone you want to have in the left hand, let go of the [Split button] before pressing a piano key.*
*Be careful not to try to test out this tone by playing a piano key while you're still holding the split button, as that will just change the split point and not select a new tone. You must let go of the [Split] button before you test out the left hand tone. If you still want to change the tone after your first selection, you can press and hold the [Split] button down again, and use the [-] and [+] buttons to select a different tone.