Touch affects how one is able to articulate notes on a keyboard, and computer-controlled haptic feedback means that this can be adjusted not only for different instruments, but also for different velocities of striking the note. This paper describes an electronic synthesizer keyboard that imitates the touch of keyboard instruments, such as pianos, harpsichords, and organs, by controlling the feedback pressure on the key as it is struck. This is an attractive idea: current electronic keyboards either have little force feedback, or attempt to imitate just one particular instrument through a mechanism that tends to be very heavy.

Details are given on how force feedback can be calculated by modeling the physical mechanism that it is simulating. The more complicated the model, the slower the simulation will be. The paper claims that modeling the components of a grand piano key is not feasible in real-time. A simplified model is developed that is a good approximation to physical mechanisms. The alternative of storing samples of force feedback from real instruments is not discussed explicitly, but it is implied that this would require too much storage for the many variations of force patterns that could occur.

The emphasis in the paper is on keeping hardware costs low. By using disk-drive motors, the estimated cost of the system is about ten dollars per key.

The effectiveness was evaluated by applying identical force patterns to both the simulated system and real instruments. The result is an impressive-looking (though unquantified) similarity between the curves showing the key position and force feedback. Because only three keys have been fully implemented, it wasn’t meaningful to get feedback from practicing musicians.

The writing style of this paper is clear, and the detailed descriptions will be of interest to anyone working in haptic feedback.