The Electro-Theremin is an electronic musical instrument developed by trombonist Paul Tanner and amateur inventor Bob Whitsell in the late 1950s to produce a sound to mimic that of the theremin. The instrument features a tone and portamento similar to that of the theremin, but with a different control mechanism. It consisted of a sine wave generator with a knob that controlled the pitch, placed inside a wooden box. The pitch knob was attached to a slider on the outside of the box with some string. The player would move the slider, thus turning the knob to the desired frequency, with the help of markings drawn on the box. This contrasts with the theremin, which a performer plays without touching as two antennas sense the position and movement of the performer's hands.

Paul Tanner was an American musician and a member of the Glenn Miller Orchestra. He developed and played the Electro-Theremin, a theremin soundalike instrument that is best known for its use on the Beach Boys 1966 songs "I Just Wasn't Made for These Times," "Good Vibrations," and "Wild Honey".