Spatial enhancement equipment for connection to existing organs or other electronic musical instruments comprises an artificial reverberation unit having coiled springs and an input transducer including a driving coil. The connection of the driving coil to the output amplifier of the organ includes a series connection of a photoresistor having a capacitor shunted across it. A variable light source applies pulses of light to the photoresistor alternately to cause it to conduct and not conduct. When the photoresistor is not conducting the electrical signals from the organ are applied to the driving coil through the shunt capacitor, introducing a phase shift into the signal. The variable light source is disclosed as a rotating disc having different patterns of opacity on it. A gating arrangement connected in parallel with the reverberation unit prevents noise from activating the power amplifier of the enhancement equipment in the absence of musical input. The gating arrangement includes a gating amplifier driving a filamentary bulb optically coupled to a photoresistor connected between the preamplifier and power amplifier of the enhancement equipment.