How do I know what key I'm in?
Playing and jamming difficulties...HELP ME!
Normally, "the key I'm in" is the open note of the Bass string. That is, the entire instrument is tuned to a particular keynote -- C, D, G, whatever.
The + frets are not there to supply notes -- not just sharps or flats -- above and beyond the diatonic scale. The 6+ fret in particular was added to the fretboard because people wanted to be able to play a C natural as well as the C# which is 'natural' to that diatonic scale.
When I first learned all this we talked about Modes, and the idea that players wanted to be able to play in more than one Mode with re-tuning. DAA (a.k.a. Ionian Mode) is what guitar folks think of as the Natural Major Scale. DAd (a.k.a. Mixolydian Mode) is almost the same -- except that the 7th note of the scale is "flatted" (a half step below what it would be in the Natural Major scale). The 6+ fret was added so that players could play both the natural and the flatted 7th note of a scale starting on the Open fret.
Years ago I wrote the attached article about modes (scales) and the diatonic nature of the dulcimer. It might help you understand things...
