The Underlever System, or Back Action
as it is commonly called, is not visible to the pianist but controls
the intricate system of levers and felt which dampen the strings
causing the sound to stop. Most vintage pianos being restored need
a new back action also, and this unique component design allows it
to be custom fitted to every model of Steinway, Mason & Hamlin,
Chickering, Knabe, and most other quality grand pianos.