<HTML>Had finished installing new strings on 6' grand piano and had chipped them close to pitch. Got out my trusty SAT Accutuner II and started at middle C, intending to work down and then up.  Accutuner worked fine until I got to Bb (2).  Then it wouldn't register the note.  I tried moving the tuner, recalibrating the FAC numbers, trying a different grand piano stored tuning.  Nothing worked.   Still registered fine above Bb(2) In experimenting I found that the lights stopped when I tuned Bb(2) exactly 1/2 step flat (in other words to A2) and all the other noted below Bb(2) the same 1/2 step flat.  I went ahead and tuned the bass by ear and then started up the piano using the same generic grand tuning I had stored in the accutuner.  When I got to Bb(5) exactly the same thing happened.  I finished the treble using the old fashioned but reliable "ear" method. When I finished this piano I went to a Baldwin Studio piano in the same church and the accutuner worked perfectly.  Went back to the grand again and had the same problem. Are you on line Dr Sanderson or Ric B.?  Or anybody that can solve this mystery. Thanks and Happy holidays to all Dick Day Marshall MI</HTML>