After 5 years, a museum with a Vough Changeable-Pitch Upright piano from the turn of the 20th century called me back for some restoration work. I’m thrilled to work on a piano like this because although the parts are old and it needs a lot of work, it is irreplaceable as only a few thousand of these were produced. It a has a changeable pitch feature that allows it to be shifted a semitone lower without re-tuning the strings. There is a lever that is currently missing that makes this shift possible. What a unique action design! Modern digital keyboards have the option to adjust the pitch center easily by pushing a button. Someone actually had to invent a way to shift the entire wooden action on the Vough to make this possible. A reason for this feature is to make it easier for pianist and singer to make music together in a comfortable range without the pianist needing to transpose the music to a different key. If it’s too high for the singer, change the pitch down, and vice versa for if it’s too low. The pitch center options are limited to two shift positions, but that was enough 100 years ago for the amateur musicians at the time.
The pitch is shifted, but the fingering remains the same. 
