Chin Rest acoustical adjustment...
(revised 8/2017)
Page AA_29
...Believe it or not, the acoustical adjustment of the chin rest can make a noticeable difference to the playability of a violin. If it is out of acoustical synchronization with the rest of the violin, it's presence on the violin will diminish the tone of the instrument. If properly tuned for the instrument, it will not have the same negative influence.
...We want the downward tap tone of the surface of the chin rest to be evenly the same as the back plate tap tone ( 198 HZ).

...Finally check to see if the horizontal area of the chin rest, where your chin actually rests, has an even tap tone. If it is too high, then sand material evenly from the bottom surface of this area until it matches. If it is too low, then sand or scrape material evenly from the edges of the horizontal area until it is raised to match the back plate tap tone.

...I want to credit Pierre Leiba for his suggestion of the value of chin rest tuning. Pierre lives and works in the Bahamas and has done good work in helping solve some of the mysteries of better violin tone, and has been helpful to me also. Good work Pierre!
...Material from underside is sanded, scraped to lower tap tone of chin support surface directly above.
Sand or scrape material from thin edges of chin rest support surface to raise tap tone from the edge toward the center. We want the vertically downward tap tone of the chin rest, all over the chin contact area, to be 198 HZ, same as the back plate.