Why do some hand turned organs have their rolls in stupid airtight compartments with a glass lid on the top?
Here again, I think we have Josef Raffin to thank for freeing the roll from its cumbersome glass case. The problem with the traditional keyless action is that the holes in the music are sensed by compressed air as it vents from the holes in the tracker bar. Unfortunately, this compressed air tends to push the roll away from the tracker bar, thereby ruining the airtight seal underneath the paper. In organs operated by cardboard book music, this problem is eliminated by a spring-loaded grooved roller which presses the cardboard hard down onto the tracker bar. This solution isn’t possible with paper music as the pressure of the roller would buckle and tear the paper, and cause it to wander off track – with disastrous results. This problem doesn’t arise with other roll operated instruments like player pianos, because they are operated by a vacuum, which tends to suck the paper onto the tracker bar and actually improves the seal. Some large paper roll pipe organs actually have a pressure su
