This started or rather progressed, evolved from soul. The 'sixties' had gone, glam rock was old hat and something new was needed. The man who played a major part in the evolution of disco as we know it was Georgio Moroder. In Germany he came across a lady who was a backing singer at the time, liked her voice and used it on a song he created from the sound of black American Soul with an English four-to-the-floor marching beat (his own description). The lady was Donna Summer and the song was I feel love.
A mushroom cloud began to grow as every producer produced a disco track for this short life music scene (it lasted about four years, 1976 to 1980) and come the early eighties everyone was fed up with it and disco became a forbidden word.
But the four-to-the floor beat has never disappeared, just the sounds around the beat changed. The term 'Disco' has come back into use now around Funky House Sounds.
The word is short for 'Discotheque', a French word meaning record-library. The word came to be as we know it during the second world war in Nazi occupied France at parties held in secret underground locations, records in great quantities were used and stored there.
This following information came from Wikipedia:
Disco is a genre of dance music. Disco acts charted high during the mid-1970s, and the genre's popularity peaked during the late 1970s. It had its roots in clubs that catered to African American, gay, psychedelic, and other communities in New York City and Philadelphia during the late 1960s and early 1970s. Disco also was a reaction by New York City's gay, as well as black and Latino communities against both the domination of rock music and the stigmatization of dance music by the counterculture during this period. Women embraced disco as well, and the music eventually expanded to several other popular groups of the time. In what is considered a forerunner to disco style clubs, in February 1970, the New York City DJ David Mancuso opened The Loft, a members-only private dance club set in his own home. Allmusic claims some have argued that Isaac Hayes and Barry White were playing what would be called disco music as early as 1971. According to the music guide there is disagreement as to what the first disco song was. Claims have been made for Giorgio Moroder's "Son Of My Father" (1972) Manu Dibango's "Soul Makossa" (1972), Jerry Butler's "One Night Affair" (1972), the Hues Corporation's "Rock the Boat" (1974), George McCrae's "Rock Your Baby" (1974). and "Kung Fu Fighting" (1974) by Biddu and Carl Douglas. The first article about disco was written in September 1973 by Vince Aletti for Rolling Stone Magazine. In 1974 New York City's WPIX-FM premiered the first disco radio show.
Musical influences include funk, Latin and soul music. The disco sound has soaring, often reverberated vocals over a steady "four-on-the-floor" beat, an eighth note (quaver) or 16th note (semi-quaver) hi-hat pattern with an open hi-hat on the off-beat, and a prominent, syncopatedelectric bass line sometimes consisting of octaves. The Fender Jazz Bass is often associated with disco bass lines, because the instrument itself has a very prominent "voice" in the musical mix. In most disco tracks, strings, horns, electric pianos, and electric guitars create a lush background sound. Orchestral instruments such as the flute are often used for solo melodies, and unlike in rock, lead guitar is rarely used. Some disco songs employ the use of electronic instruments such as synthesizers.
Well-known late 1970s disco performers included Donna Summer, The Bee Gees, KC and the Sunshine Band, The Trammps, Van McCoy, Gloria Gaynor, The Village People, Chic, and The Jacksons. Summer would become the first well-known and most popular disco artist (eventually having the title "The Queen of Disco" bestowed upon her by various critics) and would also play a part in pioneering the electronic sound that later became a prominent element of disco. While performers and singers garnered the lion's share of public attention, producers working behind the scenes played an equal, if not more important role in disco, since they often wrote the songs and created the innovative sounds and production techniques that were part of the "disco sound." Many non-disco artists recorded disco songs at the height of disco's popularity, and films such as Saturday Night Fever and Thank God It's Friday contributed to disco's rise in mainstream popularity. According to music writer Piero Scaruffi the disco phenomenon spread quickly because the "collective ecstasy" of disco was cathartic and regenerative and led to freedom of expression. Disco was the last mass popular music movement that was driven by the baby boom generation.
An angry backlash against disco music and culture emerged in the United States, hitting its peak with the July 1979 Disco Demolition Night riot. While the popularity of disco in the United States declined markedly as a result of the backlash, the genre continued to be popular elsewhere during the 1980s. Because the term "disco" became unfashionable at the start of the 1980s it was replaced by "dance music" and "dance pop" which described music powered by the basic disco beat. In the decades since, dance clubs have remained highly popular, and the disco beat has informed the sound of many of music's biggest stars. Disco has been influential on several dance music genres that have emerged since, such as House, Nu-Disco, Hi-NRG, Italo Disco, Eurodisco, Disco-Funk and Latin Freestyle.