Tracker is the generic term for a class of software music sequencers which, in their purest form, allow the user to arrange sound samples stepwise on a timeline across several monophonic channels. A tracker's interface is primarily numeric; notes are entered via the alphanumeric keys of the computer keyboard, while parameters, effects and so forth are entered in hexadecimal. A complete song consists of several small multi-channel patterns chained together via a master list.
There are several elements common to any tracker program: samples, notes, effects, tracks (or channels), patterns, and orders.
A note designates the frequency at which the sample is played back. By increasing or decreasing the playback speed of a digital sample, the pitch is raised or lowered, simulating instrumental notes (e.g. C, C#, D, etc.).
An effect is a special function applied to a particular note. These effects are then applied during playback through either hardware or software. Common tracker effects include volume, portamento, vibrato, retrigger, and arpeggio.
A track (or channel) is a space where one sample is played back at a time. Whereas the original Amiga trackers only provided four tracks, the hardware limit, modern trackers can mix a virtually unlimited number of channels into one sound stream through software mixing. Tracks have a fixed number of "rows" on which notes and effects can be placed (most trackers lay out tracks in a vertical fashion). Tracks typically contain 64 rows and 16 beats, although the beats and tempo can be increased or decreased to the composer's taste.
A basic drum set could thus be arranged by putting a bass drum at rows 0, 4, 8, 12 etc. of one track and putting some hihat at rows 2, 6, 10, 14 etc. of a second track. Of course bass and hats could be interleaved on the same track, if the samples are short enough. If not, the previous sample is usually stopped when the next one begins. Some modern trackers simulate polyphony in a single track by setting the "new note action" of each instrument to cut, continue, fade out, or release, opening new mixing channels as necessary.
A pattern is a group of simultaneously played tracks that represents a full section of the song. A pattern is intended to represent an even number of measures of music composition.
An order is part of a sequence of patterns which defines the layout of a song. Patterns can be repeated across multiple orders to save tracking time and file space.
There are also some tracker-like programs that utilize tracker-style sequencing schemes, while using real-time sound synthesis instead of samples. Many of these programs are designed for creating music for a particular synthesizer chip such as the OPL chips of the Adlib and SoundBlaster sound cards, or the sound chips of classic home computers. These programs are also often called "trackers" and are listed in this article.
Tracker music is typically stored in so-called module files where the song data and samples are encapsulated in a single file. Several module file formats are supported by popular music player programs such as Winamp or XMMS. Well-known formats include MOD, MED, S3M, XM and IT.
The first computer game to feature tracker music was Amegas (1987), an Arkanoid clone for Amiga. The music, which was composed by Obarski, is generally considered the first MOD music ever made and is well known by fans of "old school" computer music.
Most early tracker musicians were from the United Kingdom and Scandinavia. This may be attributable to the close relationship of the tracker to the demoscene, which grew rapidly in Scandinavian countries, and the relative affordability in the UK of computers able to run tracker software. Tracker music became something of an underground phenomenon, especially as so much contemporary chart music was then sample-based dance music (a genre relatively simple to produce with step-based sequencing). In fact, several chart-topping 1989/1990-era dance singles strongly foreshadow compositional trends in tracker music which would remain popular for many years to come; in particular, 808 State's "Pacific" and Octave One's "I Believe". Both tracks rely heavily on muted, detuned saw-wave background pads which play four-tone augmented major seventh chords in chord patterns which fit the pentatonic scale; an unsyncopated 4/4 drum beat runs underneath. Though this particular musical arrangement was scarcely heard earlier, an overwhelming number of tracker compositions in following years used the exact same pattern.
The popularity of the tracker format may also be attributable to its inclusion of both score data and samples. In the early 90s, the price of wavetable sound cards for personal use was very high, and the expressive capabilities of the cheaper FM-synthesizer sound cards were rather limited. A tracker requires neither of these sound card features.
The first trackers supported only four channels of 8-bit PCM samples, a limitation derived from the Amiga's Paula audio chipset. However, since the notes were samples, the limitation was less important than those of synthesizing music chips. For example, a process which became a cliché in early pop-rave chart tunes was to sample chords and play them back on a single channel. Rapid chordal stabs, often of fifths, were the hallmark of Altern-8 and other transient techno phenomena. Later tracker software, most famously OctaMED, allowed for eight or more channels, whilst special hardware could allow for 16-bit playback.
Over time, 'tracker music' became something of a term of derision for stereotypically ravey, computer-game-style pop tunes, whilst the difficulty involved in adding 'swing' to a mechanistic sequencing style resulted in much 4/4 music based around strict four-bar sections, often using similar samples. One tracker trying to address these issues is Radium; however, it is debatable whether Radium itself qualifies as a tracker at all.
Over the 1990s, tracker musicians gravitated to the PC. Although the IBM and compatibles initially lacked the hardware sound processing capabilities of the Amiga, the advent of the Sound Blaster line from Creative, PC audio slowly began to approach CD Quality (44.1kHz/16-bit/Stereo) with the release of the SoundBlaster 16.
Another soundcard popular on the PC tracker scene was the Gravis Ultrasound, which continued the hardware mixing tradition, with 32 internal channels and onboard memory for sample storage. For a time, it offered unparalleled sound quality and became the choice of discerning tracker musicians. Understanding that the support of the tracker/demo-scene would benefit sales, Gravis gave away some 6000 GUS cards to participants. Coupled with excellent developer documentation, this gesture quickly prompted the GUS to become an integral component of many tracking programs and demos. Inevitably, the balance was largely redressed with the introduction of the Sound Blaster AWE32 and its successors, which also featured on-board RAM and wavetable mixing.
The responsibility for audio mixing passed from hardware to software (the main CPU), which gradually enabled the use of more and more channels. From the typical 4 MOD channels of the Amiga, the limit had moved to 6 with TFMX players and 8 with OctaMED (both Amiga), 16 with ScreamTracker 3 on the PC, then 32 with Fast Tracker 2 and on to 64 with Impulse Tracker 2.
As such, hardware mixing did not last. As processors got faster and acquired special multimedia processing abilities (e.g. MMX) and companies began to push Hardware Abstraction Layers, like DirectX, the AWE and GUS range became obsolete. DirectX, WDM and, now more commonly, ASIO, deliver high-quality sampled audio irrespective of hardware brand.
Buzz, ModPlug Tracker, MadTracker, Renoise, reViSiT, Skale, Psycle, and others offer features undreamed-of back in the day (improved signal-to-noise ratios, automation, VST support, internal DSPs and multi-effects, multi I/O cards support etc.).
During 2007, Renoise and Modplug Tracker (OpenMPT) were the most active in development. Development is resuming on Skale and reViSiT is technically a Tracker VST plugin in the spirit of Impulse Tracker, not a stand alone program.
Tracker files have also become popular in the handheld gaming community. NitroTracker is a Fast Tracker 2 style tracker that can run directly on the Nintendo DS. The Game Boy Advance has the hardware and processing power to support tracker music, which offers good quality while taking up little space compared to MP3s or other forms of audio.
The traditional tracker stigma of unwieldy, complicated programs (aimed at a predominantly technologically-minded audience) is slowly being cast off, as programs become more accessible and user friendly. As such, tracking has recently enjoyed a mild resurgence as people begin to appreciate the importance of laying down music as quickly as possible - the musical equivalent of touch typing.
Trackers are also becoming increasingly popular with professional musicians, particularly in genres such as IDM, where fine control over sample playback is needed. Venetian Snares, for instance, has released a video on youtube of his track Tache playing in Renoise.
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