Drone music (also known as drone-based music, or simply drone) is a minimalist genre of music that emphasizes the use of sustained sounds, notes, or tone clusters called drones. It is typically characterized by lengthy compositions featuring relatively slight harmonic variations. La Monte Young, one of its 1960s originators, defined it in 2000 as "the sustained tone branch of minimalism." Music containing drones can be found in many regional traditions across Asia, Australia, and Europe, but the genre label is generally reserved for music originating with the Western classical tradition. Elements of drone music have been incorporated in diverse genres such as rock, ambient, and electronic music.

Music that contains drones and is rhythmically still or very slow, called "drone music," can be found in many parts of the world, including bagpipe traditions, among them Scottish pibroch piping; didgeridoo music in Australia, South Indian classical Carnatic music, and Hindustani classical music (both of which are accompanied almost invariably by the Tanpura, a plucked, four-string instrument that is only capable of playing a drone); the sustained tones found in the Japanese gagaku classical tradition; possibly (disputed) in pre-polyphonic organum vocal music of late medieval Europe; and the Byzantine chant's ison (or drone-singing, attested after the fifteenth century). Repetition of tones, supposed to be in imitation of bagpipes, is found in a wide variety of genres and musical forms.

The modern genre, also called drone music (called "dronology" by some books, labels and stores, to differentiate it from ethnic drone-based music), is often applied to artists who have allied themselves closely with underground music and the post-rock or experimental music genres. Drone music forms a part of the movement referred to as minimal music.

Pitchfork Media and Allmusic journalist Mark Richardson defined it thus:

The vanishing-point music created by drone elders Phill Niblock and, especially, La Monte Young is what happens when a fixation on held tones reaches a tipping point. Timbre is reduced to either a single clear instrument or a sine wave, silence disappears completely, and the base-level interaction between small clusters of "pure" tone becomes the music's content. This kind of work takes what typically helps us to distinguish "music" from "sound," discards nearly all of it, and then starts over again from scratch."

In 1949, Nouveau Réalisme artist Yves Klein wrote The Monotone Symphony (formally The Monotone-Silence Symphony, conceived 1947–1948), a 40-minute orchestral piece that consisted of a single 20-minute sustained chord (followed by a 20-minute silence)—showcasing how the sound of one drone could make music.

Composer La Monte Young is an important figure in drone music. He described himself as fascinated from a young age by droning sounds, such as "the sound of the wind blowing", the "60 cycle per second drone [of] step-down transformers on telephone poles", the tanpura drone and the alap of Indian classical music, "certain static aspects of serialism, as in the Webern slow movement of the Symphony Opus 21", and Japanese gagaku "which has sustained tones in it in the instruments such as the Sho". Young started writing music incorporating sustained tones in 1957 with the middle section of For Brass, then in 1958 what he describes as "the first work in the history of music that is completely composed of long sustained tones and silences" with Trio for Strings, before exploring this drone music within the Theatre of Eternal Music that he founded in 1962.

The Theatre of Eternal Music is a multi-media performance group who, in its 1960s–1970s heyday included at various times La Monte Young, Marian Zazeela, Tony Conrad, Angus MacLise, Terry Jennings, John Cale, Billy Name, Jon Hassell, Alex Dea and others, each from various backgrounds (classical composition and performance, painting, mathematics, poetry, jazz, etc.). Operating from the world of lofts and galleries in New York in the mid-sixties to the mid-seventies in particular, and tied to the aesthetics of Fluxus and the post-John Cage-continuum, the group gave performances on the East Coast of the United States as well as in Western Europe. These performances comprised long periods of sensory inundation with combinations of harmonic relationships, which moved slowly from one to the next by means of "laws" laid out by Young regarding "allowable" sequences and simultaneities, perhaps in imitation of Hindustani classical music which he, Zazeela and the others either studied or at least admired. The group released nothing during their lifetime (although Young and Zazeela issued a collaborative LP in 1969, and in 1970 Young contributed one side of a flexi disc accompanying an issue of Aspen magazine). The concerts themselves were influential on their own upon the art world including Karlheinz Stockhausen (whose Stimmung bears their influence most strikingly) and the drone-based minimalist works of dozens of other composers many of whom made parallel innovations including Young classmate Pauline Oliveros, or Éliane Radigue, Charlemagne Palestine, Yoshi Wada, Phill Niblock and many others.