Tone Moderator

[Robert A. Anderson]

I was tuning a Kawai NS 20-A at a church today, and the choir director
came in and asked, "What's the purpose of this hole in the back that
says "Tone Moderator."  "Tone Moderator?" I thought. So I walked around
the piano and, sure enough, there was a hole through the soundboard fit
with a plastic gizmo like a rose in a harpsichord soundboard.

I was unable to explain this. I didn't have time to mask off the hole to
see if I could detect any "tone moderation." What have you all
experienced along these lines? Perhaps Don Mannino could supply the
"official" explanation.

Bob Anderson
Tucson, AZ