A device for electrically modifying a musical tone by frequency modulation to provide effects such as the vibrato effect and the Leslie effect on the musical tone signal. The device employs a shift register through which electrical representations of the magnitude of an input signal are periodically sampled, stored, and shifted progressively through a shift register from the input to the output of the device which delays the signal. The trigger pulses which time the sampling and shifting functions of the device are frequency modulated to vary the time delay imposed, thus effecting a frequency modulation of the delayed input tone at the output of the device. In one embodiment, a digital shift register is employed which stores a digital representation of the magnitude of the signal and is connected between an analog-todigital convertor at the input of the device and a digital-toanalog converter at the output of the device. Alternatively, a bucket-brigade type analog shift register is employed which directly stores discrete analog representations of sampled input values and shifts them progressively toward the output. Plural channel devices are provided wherein the time delays are modified differently so that when the outputs of the channel are combined, an enhanced effect is provided. In a two channel device, opposite phase relationships of the modulated trigger pulse signals provide a more realistic vibrato effect.