With the fine tuning Registered Parameter Number function, the MC-303 can be tuned to match another instrument. You can also use this to detune a part to add some fatness to a particular track. Use the following messages:

Controller Value
CC101 00 Selects RPN function.
CC100 01 Selects fine tuning as the parameter you want to adjust.
CC06 XX Sensitivity in steps of 1.5 cents. The range is 0-127 with 64 being standard A=440hz tuning.