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In order to simplify the intricate wiring in known automatic bass chord systems and to reduce the number of separate decoders used therein for all chords of each key, an apparatus is provided which allows the use of only one decoder per chord type. When a chord is held one bit is applied to the inputs of a first 12-bit shaft register which correspond to the tones of the chord, after which all bits are shifted further by an HF clock pulse until this chord pattern has arrived at those outputs of the 12-bit shift register which, with the inputs of the decoder which corresponds to the chord being held, are assigned to a single pre-selected tonality.

In an electronic musical instrument with two tone generators of which the frequency of the tones produced by them is substantially constant for the first generator a priori and for the second generator not until after a final value is reached which corresponds to the frequency of the corresponding tone of the first generator, the frequency of the first generator is applied to a first input and that of the second generator to a second input of a frequency comparator circuit, whose output is connected to a control input of the second generator via control device. This ensures that the repeated readjustments of the control quantities necessary in known instruments are no longer necessary.

A device for automatic tonal accompaniment in musical instruments equipped with a rhythm unit, the fundamental, the quint, or another tone related to a chord being held and/or the chord itself becoming available in a predetermined sequence in a selected rhythm, for at least one tonal key a chord sensor is provided at whose output a signal appears in the presence of a chord, and an associated switching device is connected thereto which in the absence of a chord switches the chord sensor to detection of individual tones.

A device for electronically simulating vibrato, chorus, and pseudostereo effects and the radiation effects produced by a rotary loudspeaker with the aid of two loudspeakers or loudspeaker combinations, in which device a controllable amplifier is associated with each loudspeaker, the audio signal being applied to these amplifiers both directly and via a delay means, and both the delay and the gain of the amplifiers being varied synchronously by a subaudio-frequency generator.