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R Shepherd Consulting has used a component manufactured by NSF Controls in a high-quality computer-controlled reproducing piano.

As part of the overall electro-mechanical equipment designed into this high-resolution piano, a set of 88 special NSF tubular solenoids actuate the piano keys.

Each solenoid provides the thrust in a velocity-controlled force-actuation system capable of conveying the subtlest musical control to the piano’s hammers.

One important requirement is complete mechanical silence.

NSF Controls worked closely with Richard Shepherd to create a new bearing system for the plunger in which very close clearances combined with a soft cushion radial bearing support system are used.

The solenoid’s plungers are polished to the highest-quality finish prior to being electroless nickel plated.

This virtually eliminates any mechanical noise from linear motion.

With such tight clearances it was necessary to provide an air breather hole to eliminate pneumatic pumping effects inside the assembly.

The special linear push-shaft extends upwards via a rebound cushion assembly to a threaded head that allows adjustment with the underside of the piano key.

The shaft also extends downwards from the plunger to support a long cylindrical neodymium magnet that dips into a velocity-sensing coil beneath the solenoid: this provides feedback for controlling the hammer velocity.

To cater for very fast repeats, the solenoids are used in a closed-loop control system capable of forcing the current by factors of more than 10 for a few milliseconds.

The 1in (24mm) diameter tubular solenoids have special end-bearing rings with three m-2.5 threaded holes, enabling the solenoid to be attached to a 10mm-thick machined aluminium mounting plate, which not only serves as a communal heat-sink, but acts as a large mass into which any residual noise forces are lost.

The whole plate is rubber-mounted to the piano to isolate any vibration.

Although there are several manufacturers of reproducing pianos, this special system has been developed for professional use in a modern Steinway-D concert grand piano.

It has recently been used by Sony Masterworks in a new CD featuring the piano music of Rachmaninoff, whose key strokes were extracted from early 78rpm records by Zenph Studios in North Carolina.

This piano also ‘re-performed’ Rachmaninoff in Carnegie Hall, New York on 6 November in celebration of the 100th anniversary of Rachmaninoff’s first US recital.

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