I believe they are to help with sustain. You may remove them for tuning, but you should put them back again.
Part 2:
They aren't for sustain. Or rather, I strongly doubt that was their intent, though I used to think so. If anything, they probably were intended to mute overtones.
They debuted in 1963 with the 140A/145A/720A series and the new reed design, and were kept through the hybrid 200/200A's of 1975. They dropped them from the later 200A's.
They start exactly 1 octave down from the topmost "C", and cover 10 notes; so, there are 12 notes up top --one for each chromatic note in a scale-- that don't have them.
My best guess is that they were there to minimize a kind of murky rumble that can happen when you depress the dampers, which is especially audible in instruments with a lot of mass, like the 720(/A/B) and 726(B) furniture console series. They leave an octave of notes to act as sympathetic vibra-tors, and prevent, say, the top two C's from doubling that effect unevenly.
There are two problems with them:
1) As they cover two notes each, they make tuning those notes VERY hard--It's super-tough to align the reeds in the pickup and tighten down the two screws, and get the pressure even, etc. And you can't just get the pitch right and _then_ re-add them--they can change the pitch. You pretty much HAVE to tune those reeds flat, and do the final fine-tuning in place, with a file--if you keep them.
2) Often, especially on the 200 series, they just keep the notes from sustaining. They are typically corroded, and maybe that's why, although I suspect they were made out of some cheap metal that distorts over time. (I find that they don't do typically as much sustain "damage" in the early instruments that they were installed into.)
Most techs just take them out. If I can, I keep them in the pre-200's, but usually any theoretical benefits are so minimal, so unnoticed, that it's not worth it.
(My other hypothesis is that they are there to ease the tonal transition between the treble reeds/hammers and the midrange ones. They cover all 8 of the upper-mid reed blanks, 43 to 50, and two of the lower treble blanks, 51 and 52.)
Recent Posts