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mechanism1834
piano action1853
pianoforte action1856
key action1857
1856 Times 28 June 5/2 H. Brooks,..Pianoforte action manufacturers.
1961 C. Clutton in A. C. Baines Musical Instruments through Ages 89 The essentials of the modern pianoforte action:..double action, a check, an escapement, and an una corda mechanism.