Well now, Chris B the liverpudlian, I must respectfully disagree. I fear you are forgetting your supportive roll as an accompaniist, when you said :

..."then you have a problem with your melody instruments"...

I don't believe that there is a "problem" with anyone's playing... Lets just say that the guitar, bohdran, bouzuki, and even the piano... are translators... or cheerleaders... that can make that 'rocky road to Dublin' a little smoother... and more congenial. Yes, and everybody wins.

When sessions are getting a bit murky and undefined, finding the rhythm and 'moving' chords in a confident fluid fashion can bring it together no matter what the guitar tuning is. While it is readily apparent that the tunes themselves contain the latent rhythm and establish the beat... It is a darn good player ideed that doesn't benefit from a supportive and responsive accompaniist... and sessions... well... lets just say... all those 'correct' versions... do vary slightly...

Cheerio!
ttr