Multitrack recording (MTR), also known as multitracking, is a method of sound recording developed in 1955 that allows for the separate recording of multiple sound sources or of sound sources recorded at different times to create a cohesive whole. Multitracking became possible in the mid-1950s when the idea of simultaneously recording different audio channels to separate discrete tracks on the same reel-to-reel tape was developed. A track was simply a different channel recorded to its own discrete area on the tape whereby their relative sequence of recorded events would be preserved, and playback would be simultaneous or synchronized.

A multitrack recorder allows one or more sound sources to different tracks to be simultaneously recorded, which may subsequently be processed and mixed separately. Take, for example, a band with vocals, guitars, a keyboard, bass, and drums that are to be recorded. The singer's microphone, the output of the guitars and keys, and each individual drum in the kit can all be recorded separately using a multitrack recorder. This allows each track to be fine-tuned individually, such as increasing the voice or lowering the chimes, before combining them into the final product.

Prior to the development of multitracking, the sound recording process required all of the singers, band instrumentalists, and/or orchestra accompanists to perform at the same time in the same space. Multitrack recording was a significant technical improvement as it allowed studio engineers to record all of the instruments and vocals for a piece of music separately. Multitracking allowed the engineer to adjust the levels and tone of each individual track, and if necessary, redo certain tracks or overdub parts of the track to correct errors or get a better take. Also, different electronic effects such as reverb could be applied to specific tracks, such as the lead vocals, while not being applied to other tracks where this effect would not be desirable (e.g., on the electric bass). Multitrack recording was much more than a technical innovation; it also enabled record producers and artists to create new sounds that would be impossible to create outside of the studio, such as a lead singer adding many harmony vocals with their own voice to their own lead vocal part, an electric guitar player playing many harmony parts along with their own guitar solo, or even recording the drums and replaying the track backwards for an unusual effect.

In the 1980s and 1990s, computers provided means by which both sound recording and reproduction could be digitized, revolutionizing audio recording and distribution. In the 2000s, multitracking hardware and software for computers was of sufficient quality to be widely used for high-end audio recordings by both professional sound engineers and by bands recording without studios using widely available programs, which can be used on a high-end laptop computer. Though magnetic tape has not been replaced as a recording medium, the advantages of non-linear editing (NLE) and recording have resulted in digital systems largely superseding tape. Even in the 2010s, with digital multitracking being the dominant technology, the original word track is still used by audio engineers.

Multitracking can be achieved with analogue recording, tape-based equipment (from simple, late-1970s cassette-based four-track Portastudios, to eight-track cassette machines, to 2" reel-to-reel 24-track machines), digital equipment that relies on tape storage of recorded digital data (such as ADAT eight-track machines) and hard disk-based systems often employing a computer and audio recording software. Multi-track recording devices vary in their specifications, such as the number of simultaneous tracks available for recording at any one time; in the case of tape-based systems this is limited by, among other factors, the physical size of the tape employed.

With the introduction of SMPTE timecode in the early 1970s, engineers began to use computers to perfectly synchronize separate audio and video playback, or multiple audio tape machines. In this system, one track of each machine carried the timecode synchronization signal. Some large studios were able to link multiple 24-track machines together. An extreme example of this occurred in 1982, when the rock group Toto recorded parts of Toto IV on three synchronized 24-track machines. This setup allowed for 66 audio tracks, using track 24 of each machine for time code, and leaving track 23 blank to prevent interference with the audio.

In the late 1970s and 1980s, digital multitrack tape machines emerged, including the 3M and Mitsubishi X-800 32-track machines, and Sony DASH PCM-3324 and later the PCM-3348 machines, which allowed greater flexibility with more available tracks for recording. As well, in order to mix using automation on the console, analogue recorders generally required adjacent tracks to the time code track to be kept blank to avoid the time code signal interfering with the audio signals, which limited available tracks to 22 or 23 track at most. Digital multitrack machines had time code inserted elsewhere on the tape, and thus did not require allocating it to an audio track, which meant all tracks were available for recording. What's more, in the case of the PCM-3348, which doubled the number of tracks from the PCM-3324, both machines could use the same ½” digital tape, and also a 24-track reel first recorded on a PCM-3324 was able to be used on a PCM-3348 and have another 24 tracks overdubbed.

For computer-based systems, the trend in the 2000s is towards unlimited numbers of record/playback tracks, although issues such as RAM memory and CPU available do limit this from machine to machine. Moreover, on computer-based systems, the number of simultaneously available recording tracks is limited by the number of sound card discrete analog or digital inputs.