A form of dance music that first appeared in the mid-1970s, in New York, and was a precursor to electronica. Disco was the first style of popular music to adopt the four on the floor beat, with no beats being either accented or de-emphasized. This was often complemented with a form of bass line played in steady eighth notes, with every other note being played an octave higher, and a characteristic high-hat line in which an open hat is hit on the quarter note beat, and then closed on the following eighth note. Most disco music was vocal, although there were some notable disco tracks which were instrumental. Venues that played this form of music featured large dance floors with nattily-dressed dancers sometimes performing elaborate choreographed routines. Studio 51 in New York was a well known disco club of the era.
At its beginning, there was nothing electronic about disco; all parts were played on conventional instruments, and melody, harmony and fills were usually done using string sections and horns, in the style of production pioneered by Phil Specter in the 1950s. This all changed in 1977, when Giorgio Moroder produced singer Donna Summer's hit "I Feel Love". Moroder scrapped the Specter-ish wall of sound and replaced it with pulsing sequenced tracks from a modular Moog, and a drum machine covering the drum parts; the only part of the track not done with synths was Summer's vocals. The track was an instant club sensation, and very rapidly, disco producers began adding sequenced synths to their lineup in place of the strings, horns, and bass.
Disco's heyday came to an end around 1980, as its target audience "aged out" of the clubs, and a younger generation moved in with their punk-derived styles. However, it became a touch point for the mid-1980s bands who developed the first proto-electronica styles, and disco elements could be heard in many of these tracks, e.g., New Order's canonical "Blue Monday" contains the "octave hopping" bass line heard in many disco tracks.