I'm trying to tune my bass to C# F# B E, 1 1/2 steps down, but I dont know how many steps it goes down when you press "FLAT" on the tuner.
My GA-30 will tune down 1-5 semitones (1/2 step/one fret at a time). If your Korg is like this one, a "b" will be shown for each semitone. So for a full step, the display would show "bb" for that particular string. The instructions also note that the settings will be lost once the tuner is tuned off .