Question Does the onboard tuner in my bass amp have the ability to tune flat Answer No it does not, but you can trick it to do so. For example, to tune to Eb (Eb,Ab,Db and Gb) simply press down on the 1st fret and tune to normal E tuning (EADG) and when you release the fret, your open strings will be in Eb tuning. To tune to D fret the second fret, Db, 3rd fret, C 4th fret etc.