1) Press the [KEY ASSIGN] button.
2) Press the [JOB] button.
3) Press the  button, then press the  button.
4) Press the Instrument Key to which a Voice is to be assigned.
5) Use the [+1/YES] and [-1/NO] buttons to step through the available Voices for the selected Instrument Key.
NOTE: When the LCD displays the desired Voice, it is automatically assigned to the selected Instrument Key.
6) Press the [PATTERN/SONG] button to exit the Key Assign mode.
Reference: Owner's Manual, p.8