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The back plate viewed in indirect low angle light shows smooth transitions between various thickness areas. At this time the back plate is tuned to a (brisk tap) 'F#4' all over (two semi-tones higher than the top plate)

Now the Vigdorchik plate tuning strips are marked on the back. Notice that they are all one whole step higher than those of the top plate, that is from A3 to A4, beginning with the lowest tone at the bottom of plate.

After plate tones are established, the pencil lines are erased (as they could be seen through the 'ff' holes).