New Electronic Tuning Device for Pianos
Albert C. van der Woerd · The Journal of the Acoustical Society of America · 1972
In the tuning device being described a reference oscillator generates 84 crystal-controlled frequencies, which follow a stretched scale whose deviations are programmed in an interchangeable diode matrix. Three different diode matrices have been realized, intended for tuning small, medium-size, and grand piano's, respectively. A bandpass filter is used, the transmission range of which automatically follows the reference frequency. An electromagnetic device is used as a sound transducer. In consequence of this, tuning of all strings on their fundamentals becomes fully feasible. With one medium-size piano, the achieved accuracy was measured. The accuracy of the tuning with respect to the reference frequency was <10−4 in all cases. The total accuracy (including the inaccuracy of the reference oscillator) varies from 10−4 for the lowest note to 5×10−4 for the highest note.