And then maybe they can put up a second sign right next to it showing:

All possible accordion keys:
G, G#, A, B, Bb, C, C#, D, Eb,E, F, F#

Tunings:
Straight/Just Cajun Tune w/ Tempered 3rds & 7ths, wet or dry

Equal temperament Tuning

Zydeco Tuning, wet or dry.

Now that wasn't so hard now was it?

I sure hope the link I posted works. It shows Kaleb Leday demonstrating the same exact song in 3 different keys/positions using a B Natural accordion.....using the Nashville Number System that puts him playing the song in the 4th (E), the 5th (F#), and on the 1 (B).

The description on facebook is: Lessons By LeDay #MondayMadness "3 major keys per 1 accordion"
https://www.facebook.com/share/v/1A9bNbnHtD/

Listen to the "RESONANCE" of this B natural and how the resonance is most dominant when he plays in the 5th which is in F#. Truly remarkable use of chords! And be sure to read his description of what he's doing. Awesome!