Circuit for modulating a musical tone signal to produce a rotating effect

Apparatus for electronically modulating a musical tone signal to produce an effect which simulates the radiation of sound by a rotary loudspeaker, comprising:

• means for generating a sub-audio frequency, substantially sinusoidal, modulating signal;
• a single frequency modulator responsive to said modulating signal to modulate the frequency of said musical tone signal;
• means connected to the output of said frequency modulator for applying the tone signal modulated substantially only in frequency to a first stationary transducer for converting said frequency modulated signal into sound;
• a single amplitude modulator responsive to said modulating signal to modulate the amplitude of said musical tone signal, said amplitude modulator producing an amplitude-modulated tone signal only during positive half-cycles of said modulating signal;
• and
• means connected to the output of the amplitude modulator for applying the tone signal modulated substantially only in amplitude to a second stationary transducer for converting said amplitude-modulated signal into sound;
• the phase relationship of the modulating signal applied to said frequency modulator and to said amplitude modulator being such that the amplitude-modulated signal has maximum amplitude when the frequency modulated signal is in transition from sharp to flat relative to the musical tone signal and has substantially zero amplitude when the frequency modulated signal is in transition from flat to sharp;
• said first and second transducers being positioned sufficiently proximate each other that the sounds separately produced by thereby are acoustically mixed.

Apparatus for electronically modulating a musical tone signal which modulated signal when converted to sound produces an effect which simulates the radiation of sound by a rotary loudspeaker, said apparatus comprising:

• means for generating a sub-audio frequency, substantially sinusoidal, modulating signal;
• a first signal channel having therein an amplitude modulator connected to receive said musical tone signal and operative in response to said modulating signal to produce an amplitude modulated output signal only during positive half-cycles of said modulating signal, and including first transducer means for converting the amplitude modulated tone signal into sound;
• a second signal channel having therein a frequency modulator connected to receive said musical tone signal and responsive to said modulating signal to modulate the frequency of the musical tone signal and produce a frequency modulated output signal which goes from sharp to flat relative to the musical tone signal during periods that an amplitude modulated tone signal is produced in the first channel, and which goes from flat to sharp during periods that no amplitude modulated tone signal is produced in the first channel, and including second transducer means for converting the frequency modulated tone signal into sound;
• said first and second transducer means being positioned sufficiently proximate each other that the sound therefrom is acoustically mixed, the acoustically mixed sound from the two channels producing radiation effects simulative of that produced by a rotary speaker.