The way I understand Cajun accordion tuning is that the accordion is tuned to just intonation instead of the generally used equal temperament and that the thirds (E's and B's) are tuned flat anywhere from 10 cents to 15 cents. Also, sometimes the fourth (F's) are tuned sharp.
Anyone have any more specific information regarding tuning or a link to a site explaining the specific tuning pattern?
What I've been doing on the last few is the 3rd's and 7th's tuned 14 cents flat, the 4ths tuned 10 cents sharp. I've heard the reasoning in not sharpening the 4ths is for those who like to play in F (on a C) with accompaniment, so it doesn't sound to off. I like the 4th chord, so I tune 10 cents sharp with the thought that maybe that will sound less "off" in the rare times I play that key with accompaniment. Everything in diatonic accordions is a compromise