Short answers, pulled from the story.
The first electronic musical instrument to achieve public recognition was the Telharmonium, unveiled at the turn of the 20th century. This device, developed by Thaddeus Cahill, synthesized the sounds of orchestral instruments with surprising precision using massive electrical machinery.
Halim El-Dabh created The Expression of Zaar, believed to be the earliest tape music composition, in 1944. He processed recorded sounds of an ancient zaar ceremony using reverberation, echo, and voltage controls at the Middle East Radio studios in Cairo.
Karlheinz Stockhausen composed Studie I in 1953, followed in 1954 by Elektronische Studie II, the first electronic piece to be published as a score. This work emerged from the WDR studio in Cologne, which officially opened in 1953.
Yamaha introduced the first stand-alone digital synthesizer, the DX7, in 1983. This instrument used FM synthesis and became one of the best-selling synthesizers of all time with its recognizable bright tonalities.
The Moog synthesizer was brought to the mainstream in 1968 by Switched-On Bach, a bestselling album of Bach compositions arranged for Moog synthesizer by American composer Wendy Carlos. The album won the 1970 Grammy Awards for Best Classical Album, Best Classical Performance, and Best Engineered Classical Recording.
Patrick Gleeson pioneered the use of synthesizers in a touring context by playing live with Herbie Hancock at the beginning of the 1970s. This work subjected the early machines to stresses they were not originally designed for.