Clark, There are two systems that seem to work for quiet back rail/key noise. The first is to not have the back rail cloth glued down in the "contact" area, where the key end meets the felt. (as in a flat surface area). The second, is what I would call the "Steinway" back rail method, which is a crowned surface. This is accomplished by gluing both the front and back edges of the "top" layer of felt into groves in the key frame. Underneath the top layer is unreinforced felt that makes the top layer "crown". IMO the "crowned" method is more effective, but more difficult to do. I hope I have explained this properly. Hopefully, some others will "Chime In". Regards, Joe Garrett, RPT, (Oregon)
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