A music sequencer (or simply sequencer) is a device or application software that can record, edit, or play back music, by handling note and performance information in several forms, typically MIDI or CV/Gate, and possibly audio and automation data for plug-ins and DAWs.

As mentioned above, musical sequencers are often categorized by handling data types, as following:

Also music sequencer can be categorized by its construction and supporting mode.^{[clarification needed]}

With the advent of MIDI and particularly Atari ST in 1980s, programmers were able to write software that could record and play back the notes played by a musician. Unlike the early sequencers used to play mechanical sounding sequence with exactly equal length, the new ones recorded and played back expressive performances by real musicians. These were typically used to control external synthesizers, especially rackmounted sound modules as it was no longer necessary for each synthesizer to have its own keyboard.

As the technology matured, sequencers gained more features, and integrated the ability to record multitrack audio. Sequencers mainly used for audio are often called digital audio workstations (or DAWs).

The sound barrier, in aerodynamics, is the point at which an aircraft moves from transonic to supersonic speed. The term, which occasionally has other meanings, came into use during World War II, when a number of aircraft started to encounter the effects of compressibility, a collection of several unrelated aerodynamic effects that "struck" their planes like an impediment to further acceleration. By the 1950s, new aircraft designs routinely "broke" the sound barrier.

Some common whips such as the bullwhip or sparewhip are able to move faster than sound: the tip of the whip breaks the sound barrier and causes a sharp crack—literally a sonic boom.Firearms since the 19th century have generally had a supersonic muzzle velocity.

The sound barrier may have been first breached in nature some 150 million years ago. Some paleobiologists report that, based on computer models of their biomechanical capabilities, certain long-tailed dinosaurs such as Apatosaurus and Diplodocus may have possessed the ability to flick their tails at supersonic velocities, possibly used to generate an intimidating booming sound. This finding is theoretical and disputed by others in the field. Meteorites entering the Earth's atmosphere usually, if not always, descend faster than sound.