Instruments producing audio signals without air being involved in generating sound waves are known as electrophones. Some of the most common types of electrophones are:
1. Theremin: The Theremin is one of the earliest electronic musical instruments. It uses two antennas to sense the position of the performer's hands and produces sound by varying the frequency and amplitude of an oscillator circuit.
2. Ondes Martenot: The Ondes Martenot is a French electronic musical instrument that uses a keyboard to control the pitch of an oscillator. The performer also controls the timbre and volume by moving a metal ring around a metal rod.
3. Mellotron: The Mellotron is an electro-mechanical musical instrument that uses pre-recorded tapes to produce sound. The tapes are played back at different speeds to create different pitches.
4. Chamberlin: The Chamberlin is a similar instrument to the Mellotron, but uses magnetic tape instead of pre-recorded tapes. This allows for more flexibility in creating sounds.
5. Hammond organ: The Hammond organ is an electric organ that uses a rotating tonewheel to produce sound. The tonewheel is interrupted by a series of magnets, which causes the sound to be modulated.
6. Moog synthesizer: The Moog synthesizer is an analog synthesizer that was first developed in the 1960s. The Moog synthesizer can be used to create a wide variety of sounds, from simple waveforms to complex sound effects.
7. Synthesizer: A synthesizer is an electronic musical instrument that can produce a wide variety of sounds by combining different waveforms, frequencies, and modulations. Synthesizers can be analog, digital, or a hybrid of both.