Modulation is the process of changing a parameter such as volume, pitch, or filter cutoff over time by using another signal or performance control. It adds movement and expression to a static sound and can create vibrato, repeated motion, or changes that follow each note.
Source and destination
The signal that creates the change is the modulation source, and the parameter being moved is the destination. Common examples include an LFO controlling pitch, an envelope opening a filter, and velocity controlling volume.
Common modulation sources
An LFO creates periodic movement, while an envelope shapes a change across the duration of each note. A modulation wheel, aftertouch, and MIDI CC data can control the amount during a performance or through automation.
Depth and direction
Amount or Depth determines how far the destination moves. Many instruments allow both positive and negative modulation. Raise the depth until the effect is easy to identify, then reduce it to the amount that works in the music.
How it differs from automation
Automation records or draws parameter values directly along the song timeline. Modulation applies a relative change from another signal such as an LFO or performance control. Combining them lets the base value move through the arrangement while smaller variations continue around it.
Points to watch
Several sources controlling one destination can make the final value difficult to understand. Enable one route at a time in the modulation matrix and check for unintended changes in level, pitch, or stereo width. For changing from one musical key to another, see Modulation as a music-theory term.
