A gate stays high for a note's duration; a trigger is a brief pulse that fires one event

Gates and triggers are both binary on/off voltage signals (0 V for off, a positive voltage — commonly 5 or 10 V — for on), distinguished by duration and purpose. A gate goes high when a key is pressed or a sequencer step is active and low when released, so its length mirrors the held note; envelope generators read a gate to know how long to sustain — an ADSR passes through attack and decay, holds at the sustain level while the gate is high, and releases when it drops. A trigger is a very short pulse (typically around one millisecond) that fires an instantaneous event regardless of how long the source is held: advancing a sequencer, starting a drum hit, resetting a clock; a clock is just triggers repeated at a steady tempo. Triggers suit AD/decay-style percussive envelopes, which complete on their own. Because a decay-only envelope ignores hold length, it does not care which it receives, but a sustaining ADSR does. Confusing the two is a common patching error: feed a long gate where a momentary trigger is expected, or vice versa, and timing or retriggering behaviour goes wrong.

Examples

A keyboard gate to a lead synth’s ADSR (or to a VCA CV input) holds the note open while the key is down and closes on release. A sequencer step’s trigger to a drum module fires one hit per step regardless of step length. Feed a 4-beat gate into a drum module expecting a trigger and the retriggering/timing behaviour is wrong.

Assessment

State the difference in duration and role between a gate and a trigger. Name two module types that expect triggers and two that expect gates. Explain why a decay-only envelope does not care which it receives while a sustaining ADSR does, and predict what happens when a 4-beat gate is fed to a trigger input.