In traditional Cajun Accordion playing if the accordion is a Bb, what Guitar chords are being played for most part on tunes. Isnt it F and C, Bb? Any suggestions?

If you are playing in the key of F The I is F the IV is Bb and the V is C.

If you're playing in Bb the I is Bb the IV is Eb and the V is F.

those are your chords ! your guitar player could also capo the 4th fret and play in the G, C, F, and D formations and get the same chords.

hope this helps and I hope you know what I IV V is !!

If I am not mistaken the Bb capo position is on the third fret..

You are correct Karl, Thanks.

woops !

lots of guitar players like A and E
capo in first fret works for that
bflat becomes a
eflat becomes e
etc