Open G# mechanism This is a fingering system which works in the opposite way to the more common closed G# system.  When the player plays ‘G’ fingering, this instrument will actually sound G#.  To play ‘G’ the left hand small finger needs to be put down.  It is a more logical system in that to ‘go down’ the chromatic scale the player adds another finger.  In fact is was Theobold Boehm’s original system, along with reversed thumb keys, and is played in eastern block countries to this day.  Many western players have adopted the Open G# system without reversing the thumbs.