Tracker
A tracker is a sequencer that shows music as a vertical grid of text: time runs downward, each column is an instrument or voice, each line is a note division, and the cells hold notes, parameter values, and effect commands as numbers. You type into it. Where a piano roll draws pitch against time as blocks, a tracker spells the same information out — “note, parameter and effect changes” per line attack-mag-5-trackers.
Trackers began on the Commodore Amiga: Ultimate Soundtracker (1987) was the first, OctaMED the most widely used. The form survived the Amiga by moving into software DAWs and, more recently, back into hardware.
The interface is the argument
A tracker’s defining property is that editing granularity is per-line and typed. That makes fast, dense parameter movement cheap — “pitch rolls, volume swells and other quick changes” cost a number in a column rather than a drawn automation curve — which is the mechanism behind the form’s association with jungle, breakcore and IDM. The interface didn’t merely suit those genres; the cheapness of the gesture is why the gesture became idiomatic.
The cost runs the other way for anything smooth or performed. A tracker is a poor place to record a feel, and the vocabulary of effect commands has to be memorized before the speed arrives. The roundup that seeds this page pushes back on the reputation (“not all that hard,” not only for fast music) without disputing the shape.
Not an engine
“Tracker” says nothing about how sound is made — a tracker can drive samples, FM, chiptune, or plugins. SunVox is a modular synthesizer (modular-routing) with a tracker for a sequencer; Renoise is a full DAW with plugin hosting; the Dirtywave M8 and Polyend Tracker+ are grooveboxes whose sequencer happens to be a grid of text. This puts the class beside chord synths rather than beside synthesizer or sampler: both are categories defined by how you address the music, not by what makes the sound.
Related
attack-mag-5-trackers · daw · sampler · modular-routing · chord-synthesizer · midi-controller · synthesizer