I know we have had discussions concerning blunders we have made. Here is mine from this morning's Mass. I was singing the communion hymn "Eat This Bread" and have always sung the alto part every time with the choir. I went over the hymns last evening just to make sure all was well. HOWEVER, when the introduction was played by the organist, I opened my mouth and sang the alto line even though I was looking at the melody line. The organist is a singer as well and he turned on the mike which he uses when he has to both sing and play. So it became a duet! I am not really musically trained and don't have perfect pitch, so I guess like Pavlov's dog I heard the intro I had heard before and sang the part I always sang. Bit of a nightmare for a few seconds!