Abstract: An electronic keyboard instrument generates signals of frequencies respectively corresponding to keys by depressing the keys of a keyboard from a signal source, and reproduces a musical note corresponding to the generated signal. The frequency spectrum of an external signal is detected and used to control the frequency spectrum of the generated signal to cause the frequency spectrum of the generated signal to approximate that of the external signal.

Abstract: An electronic tuner for musical instruments is disclosed which has built therein a voltage-controlled reference oscillator having its oscillation frequency controlled by a control signal and in which the oscillation signal of the reference oscillator and an input musical sound signal from a microphone are phase compared by a phase comparator and the oscillator is controlled by the phase compared output so that its oscillation frequency is synchronized with the frequency of the input musical sound signal. A control voltage, which is obtained when the oscillation frequency of the reference oscillator is synchronized with the frequency of the input musical sound signal, is applied to an indicator to indicate the ratio between the two frequencies.