Electromechanical musical instrument

What is an electromechanical musical instrument?

An electromechanical musical instrument generates electrical signals using mechanical components. These signals are then electronically processed, amplified and made audible as sounds via loudspeakers. The rotating or vibrating components initially generate mechanical energy, which is converted into electrical energy to produce sounds. Instead of electromechanical instruments, sound generation could also be referred to as mechano-electrical instruments. However, this term is not common.

Examples of this are the electric guitar, the Hammond organ and the telharmonium. On the electric guitar, the body and the strings vibrate, while on the Hammond organ an electric motor drives a rotating mechanism. In both cases, electromagnetic pickups use vibrations as sensors and convert them into sound signals.

History of electromechanical musical instruments

The telharmonium (also known as the dynamophone) was an early electromechanical musical instrument. Thaddeus Cahill, an American, received the patent for this invention in 1897. As with the later Hammond organ, iron gear wheels (tone wheels) rotated in front of a coil with a permanent magnetic core in the Telharmonium and generated an electric current through induction. This current was made audible and produced sine tones. The instrument weighed up to 200 tons and only three examples were built.

Electromagnetic pickups generate electricity through induction. The pickup for the electric guitar was developed in 1931. Laurens Hammond received a patent for his organ in 1934. The Hammond organ was presented to the public the following year.

Principle of electromechanical musical instruments

The mechanical component

A central principle of electromechanical musical instruments is the mechanical component that is responsible for producing the sound. In the Hammond organ, for example, rotating tone wheels, similar to cogwheels, are the driving force. An electric motor sets these tone wheels in motion and thus produces the characteristic sound.

However, there are also electromechanical instruments that work without electric motors. Instead, the sound is produced by vibrating mechanical components. This can be, for example, a string that is plucked with a finger or a pick, as on an electric guitar. This also includes sound plates or reeds that are struck using a piano-like mechanism, as with the Fender Rhodes. Another variant is a reed that is struck by a mechanism similar to a harpsichord, as is the case with the “Weltmeister” claviset. When picking up sound by induction, the rotating or vibrating component must be ferromagnetic.

Sound pickup

This can be done in various ways:

Inductive, for example, when the rotating or vibrating medium changes the magnetic field of an electrical generator.

Capacitive, if the oscillating medium corresponds to a capacitor electrode that is part of an electrical oscillating circuit.

Or piezoelectric, when the vibrating medium is mechanically attached and causes a piezoelectric reaction. These different methods of sound pick-up enable efficient conversion of the generated sounds into electrical signals, which can then be further processed and amplified.