StroboSoft™ can be used to tune accordions since it has a chromatic mode. Any offsets can be measured since the display will tell you how many cents you are out of tune in real-time while it displays the note simultaneously.
StroboSoft contains preset temperaments for tuning in the 12-tone scale. Equal temperament may be the best choice in most cases.
In the event you have an accordion that requires tuning on a Well-Tempered scale, StroboSoft offers 7 different Well-Tempered presets to assist you.
Additionally, StroboSoft offers an extremely wide Concert A range....340Hz to 540Hz. So if you are looking to tune outside of the standard A440Hz, no worries. German style, polka style, Italian sounding tunings...no problem!
We do not have presets for accordion in StroboSoft Deluxe, but depending on what type of accordion you are tuning (4/5 for example), you can create a preset by selecting an instrument preset that offers at least nine strings (StroboSoft contains a Lap Steel preset that offers 10 locations for storing unique tuning values for each string...or reed in your case.) It is a way to work around and sort of "trick" SS into being your own custom accordion tuner.
You can store an unlimited amount of presets also. These presets can contain the absolute tuning values for particular reeds, offsets for each reed set if desired, and a temperament for the complete tuning all under your own custom name. You will not, of course, have an accordion as a visual graphic (instrument mode displays a graphic of the instrument.)...minor drawback.
You will require the Deluxe version of the software to store presets.