Melani---you're not alone in the key of "f". I do a lot of my work self-accompanied on the accordion, and have done so for so long that my playing is almost restricted by my voice range. In other words all those years back I learned to play by ear on the key which suited my own voice for the individual piece. The end result has been a proficiency in the keys of "c", "g", and "f", those being the keys with which I can cover nearly any song I want to sing. In fact I used to drive trained musicians wild by being over fond of "F-sharp"! Not alone on that either---I have heard the Corries use it many a time. I tend NOT to use the "box" in any other key when in concert with other musicians, as I don't feel competent to do so, other than "vamping" on the bass keys on occasion.