[Zubersoft]

Thanks - I look forward to reviewing the algorithm. I do want Johan (sciurius) to be a part of this conversation as well, because the ChordPro application behaves in the exact same way. If I have a song with a [B/D#] chord and I apply {transpose: -2}, the output shows A/Db.  If I transpose with -3 (to the key of E), it then shows Ab/C, just like MobileSheets. So the two applications are behaving identically. If the approach is fundamentally wrong, then both applications need to be fixed to transpose in the correct manner. My code is not set up to handle B# as a valid chord I believe, so that's something that would have to change, but it definitely creates a lot of annoying problems, as it's still not clear to me when I would use B# versus C in all situations. 

Mike