Question: When was the electronic musical instrument controlled without physical contact by the thereminist, developed?

Context articles: Theremin
Timeline of music technology
Synthesizer
Sound module
Omnichord
Electric instrument
Magnetic bearing
AlphaSphere (instrument)
Hydraulophone
Electronic musical instrument

The theremin ( ; originally known as the ætherphone/etherphone, thereminophone or termenvox/thereminvox) is an electronic musical instrument controlled without physical contact by the thereminist (performer).
 It is named after the Westernized name of its Soviet inventor, Léon Theremin (Термéн), who patented the device in 1928.
The timeline of music technology provides the major dates in the history of electric music technologies inventions from the 1800s to the early 1900s and electronic and digital music technologies from 1917 (the date of the Theremin's development) and electric music technologies to the 2010s.
A synthesizer (often abbreviated as synth, also spelled synthesiser) is an electronic musical instrument that generates electric signals that are converted to sound through instrument amplifiers and loudspeakers or headphones.
 Synthesizers may either imitate instruments like piano, Hammond organ, flute, vocals; natural sounds like ocean waves, etc.; or generate new electronic timbres.
 They are often played with a musical keyboard, but they can be controlled via a variety of other input devices, including music sequencers, instrument controllers, fingerboards, guitar synthesizers, wind controllers, and electronic drums. Synthesizers without built-in controllers are often called "sound modules", and are controlled via USB, MIDI or CV/gate using a controller device, often a MIDI keyboard or other controller.
A sound module is an electronic musical instrument without a human-playable interface such as a piano-style musical keyboard.
 Sound modules have to be operated using an externally connected device, which is often a MIDI controller, of which the most common type is the musical keyboard (although wind controllers, guitar controllers and electronic drum pads are also used).
 Controllers are devices that provide the human-playable interface and which may or may not produce sounds of its own.
 Another common way of controlling a sound module is through a sequencer, which is computer hardware or software designed to record and play back control information for sound-generating hardware (e.g., a DJ may program a bassline and use the sound module to produce the sound).
 Connections between sound modules, controllers, and sequencers are generally made with MIDI (Musical Instrument Digital Interface), which is a standardized protocol designed for this purpose, which includes special ports (jacks) and cables.
The Omnichord is an electronic musical instrument introduced in 1981 by the Suzuki Musical Instrument Corporation.
 It typically features a touch plate, and buttons for major, minor, and 7th chords.
 The most basic method of playing the instrument is to press the chord buttons and swipe the touch plate with a finger or guitar pick in imitation of strumming a stringed instrument.
 Originally designed as an electronic autoharp substitute, the Omnichord has become popular as an individual instrument in its own right, due to its unique, chiming timbre and its value as a kitsch object.
An electric musical instrument is one in which the use of electric devices determines or affects the sound produced by an instrument.
 Electric musical instruments are an example of electric music technology.
 It is also known as an amplified musical instrument due to the common utilization of an electronic instrument amplifier to project the intended sound as determined by electric signals from the instrument.
 Two common types of instrument amplifiers are the guitar amplifier and the bass amplifier.
 This is not the same as an electronic musical instrument, like a synthesizer, which uses entirely electronic means to both create and control sound.
A magnetic bearing is a type of bearing that supports a load using magnetic levitation.
 Magnetic bearings support moving parts without physical contact.
 For instance, they are able to levitate a rotating shaft and permit relative motion with very low friction and no mechanical wear.
 Magnetic bearings support the highest speeds of all kinds of bearing and have no maximum relative speed.
AlphaSphere is an electronic musical instrument that was designed and developed by nu desine, an award winning company based in Bristol, UK.
 The primary concept of the AlphaSphere is to increase the level of expression available to electronic musicians, by allowing for the playing style of a musical instrument.
 Even before the product had been fully developed it had appeared at many events worldwide including the NAMM Show, Musikmesse, TEDx conferences, and the Future Everything Festival, and received press from popular organisations such as Sound on Sound, BBC, Wired and MusicRadar.
 There are currently two different AlphaSphere models - the nexus series and the elite series.
A hydraulophone is a tonal acoustic musical instrument played by direct physical contact with water (sometimes other fluids) where sound is generated or affected hydraulically.
 Typically, sound is produced by the same hydraulic fluid in contact with the player's fingers.
 The term also refers to an acoustic sound-producing mechanism used as an interface or input device involving the monitoring of fluid flow.
 Examples include hydraulophones for fluid-flow monitoring and measurement applications, such as building automation, equipment monitoring, and the like (for example, determining which faucet or toilet in a building is operating and how much water it is consuming).
 The hydraulophone in the first sense was invented and named by Steve Mann, and has been used as a sensory exploration device for low vision individuals.
 Hydraulophones around the world are designed by Splashtones Music.
An electronic musical instrument is a musical instrument that produces sound using electronic circuitry and/or digital devices.
 Such an instrument sounds by outputting an electrical, electronic or digital audio signal that ultimately is plugged into a power amplifier which drives a loudspeaker, creating the sound heard by the performer and/or listener.