You can like Maxence said, and how is not very obvious in the manual
How can be found in the section getting started
Look for the section quick settings : you will get at quick setting bij pressing the aodyo symbol at the front.
Now press and hold the highest key at the back, and now one can change the base key with the Increase and decrease keys ( D settings key)
Once you have tried, you will wonder why you have not seen it before, it is that simple