GB1213794A - Tuning of musical instruments - Google Patents

Abstract

1,213,794. Tuning musical instruments; measuring frequencies. R. S. PHILLIPS. 5 March, 1968 [5 Dec., 1966], No. 54377/66. Heading G4A and G5J. In an apparatus for use in tuning a musical instrument, a pulse of duration proportional to the frequency of a note is derived from a signal A produced by a transducer 7 and applied to open a gate through which high frequency oscillations are applied from a generator 13 to a binary counter 14. The counter is initially set to the complement plus one of the correct count for the note by means of a note selector switch 5 and a diode matrix 17 (Fig. 4, not hown), whereby the counter is returned to zero if the instrument is in tune. Otherwise the final reading of the counter indicates the departure from correct tuning. At the completion of each count the counter reading is transferred by a monostable circuit 18 to a lamp display 6 and a meter system 8, 15. In order that the counter may function in the same frequency range for all octaves, the circuit between transducer 7 and gate 12 includes a switched divider system 4, 10 whereby between one and seven binary dividers may be introduced. A final divider 11 halves the frequency of the gate signal. The input signal to 11 triggers a monostable circuit 16 so as to operate 5 and 17 to set in the initial count before each count, whilst the output signal from 11 resets circuit 16 and triggers circuit 18. The lamp display comprises five lamps of which the centre lamp, when illuminated, indicates that the instrument is in tune, whilst the two adjacent lamps respond to a count error of between one and sixteen and the outer lamps to an error of more than sixteen.