I have Seiko 747 chromatic tuner which is very helpful. A couple of my recorders seem to be always a shade flat no matter what I do. The tuner gives me the option of tuning A at anywhere between 435 and 446. So I can find out where the recorder is and tune the guitar to that A. Its so much nicer. I am using it also to help me train my ear as I try and tune by ear first and then check with the tuner. Slowly, oh so slowly, I'm getting better.