The avant-garde was also concerned with electronics.

Composers were not only trying to find new ways of dealing with existing timbres and sounds, but to go one level higher: to invent sound itself. They wanted to achieve colors that did not exist in the physical world, and to go beyond the concept of the "note".

https://www.youtube.com/watch?v=mS6tv50YGWg - Youtube to Mp3

The German avant-garde musician Karlheinz Stockhausen (1928-2007) is considered the pioneer of electronic music. His first experiments in this field took place in the early 1950s, when electronic sounds were not yet part of pop culture.

Today we are used to seeing synthesizers and controllers at rock and pop concerts, and we perceive electronic music as part of the club dance esthetic. But it began as an avant-garde experiment in the context of intellectual academic music. For example, the pioneers of electronic sound in pop culture unanimously named Stockhausen as one of their teachers.

There are several directions in electronic academic music. 

The so-called tape music. "Music for electronic tape" - involves the manipulation of musical sounds or those artificially created with a noise generator. In the first case, it is sampling - working with short, pre-recorded fragments. In the second case, it is the synthesis of sounds. They are mixed, collaged, distorted with filters and speed changes, "cut up" and looped. The result is a kind of sound canvas, an artifact stored on an electronic medium, but which can also be played live on stage.

https://www.youtube.com/watch?v=RpSO3UHKy_g -  Youtube to Mp3

There is an area of tape music that is called "musique concrete" (concrete music) in French. Concrete music involves working with recordings of non-musical sounds from the physical world - human voices, mechanical and natural sounds.

Of course, "tape music" is not a work played according to notes, but a kind of total sound state in which the listener is immersed. For this reason, the space in which the tape is played and the way the speakers are arranged within it may also be part of the composer's intention. This is where tape music meets the art of sound installation and sound design.

Another type of electronics involves the simultaneous sound of live instruments and a tape recorder. These can be "cosmic" artificial sounds or pre-recorded sounds of the same instrument played by a live musician - creating a beautiful and uncanny effect of doubling, twistingand verifying the performer.

https://www.youtube.com/watch?v=4bHnGorNTT0  - Youtube to Mp3

An important name in academic electronics is the Greek genius Yanis Xenakis (1922-2001). Since ancient times, the enlightened world has debated the close connection between music and mathematical science. Two and a half millennia later, Xenakis was the successor of his compatriot Pythagoras, who spoke of the calculability of musical phenomena. Xenakis was concerned with sound synthesis on the computer and developed interfaces, i.e. ways for the computer to communicate with the user. The composer's most important tool was a computer with a graphics tablet that converted graphic information into sound information (in other words, symbols and drawings into sounds).

Avant-garde composers in the United States handled electronics quite differently. American composers also created artificial sounds. But they were much more interested in making electronic experiments with natural and man-made spaces, investigating the sound properties of objects and items in the physical world. They enjoyed using electronics to control the acoustics of a room, the echo effect, resonance, reverberation and the way different objects conduct sound. Listen to the meditative audio installations of Pauline Oliveros (1932-2016) or the music of Alvin Lucier (b. 1931) and discover how a room, a teapot or a piano string stretched between walls sounds.

https://www.youtube.com/watch?v=WFJZUaeqOsc  - Youtube to Mp3

Tape music is a field of electronic music in which a work is a collage of artificially pre-recorded and synthesized sounds. They are manipulated in various ways: cut into loops, played at different speeds, etc.

Dictionary 

• Concrete music - a field of electronic music in which sounds recorded on tape from the environment are used.
• Sampling - the use of short, tape-recorded "samples" (samples) of a sound.
• Synthesis - the creation of artificial sounds by machines.

Examples:

Karlheinz Stockhausen, Janis Xenakis, Pierre Schaeffer, Pauline Oliveros, Alvin Lussier