Impulse Tracker is a multi-track digital sound sequencer which proliferated on the DOS platform. It was authored by Jeffrey Lim. The software was distributed as freeware, though the author supplied extra features (like saving stereo WAV files, possibility to use an IPX network mode) in exchange for some cash. Once the stereo WAV writer plugin was publicly pirated, the author announced that he will and discontinue it after version 2.14. (There were some patches released, and 2.15 is by outsider contributors.) Impulse tracker's interface was very similar (and could be considered the continuation of) ScreamTracker 3. It was comparable to its rival FastTracker.
Like most MOD editors music is arranged into a grid of channels, each channel containing key-on and optional key-off instructions not unlike MIDI. The Impulse Tracker modules have an extension of .IT.
One of the features which set this MOD editor apart was NNAs, New Note Actions. If a new key-on command is received in the same channel as another instrument which is still being played, NNAs allow the user to customize the action that next occurs:
- Cut: New instrument sound replaces current playing instrument.
- Continue: Old instrument continues to play following its defined ADSR curve.
- Off: Old instrument instructed to begin release section of its ADSR curve.
- Fade: Old instrument fades out to 0 volume at a designated rate overriding any ADSR information.
Cheesetracker is a GPLd Impulse Tracker clone, which runs under Linux and Mac OS X.