I remember singing with a small group many years ago. The lead tenor had a soaring voice and great confidence in it. My difficulty was that he always sounded about 1/8 tone flat on the high notes - just enough to be like nails on a blackboard to me. It became a sore point with both of us, young and headstrong as we were.

I have heard a number of passages in vocal recordings over the years, some from very admired and respected groups and soloists, which had that same effect on me. To this day, I am not entirely certain whose ear was just so slightly off. I CAN say that when I hear a chord that is spot-on, vocal or instrumental, it is crystal clear to my ear and quite pleasant.