Modulation effects are a particular category of audio effect (FX).
These are effects which modify the sound in a certain way: by adding a time-delayed version of the sound to itself, and then varying the size of that delay over time.
Although this same process is common to all modulation effects, it can create a huge range of sounds! Audio effects ear training can let you learn to hear the different types of modulation effect, and even the parameters used to configure each one.
Some of the details which determine the kind of audio effect produced include:
- How long the delay is (e.g. 10 milliseconds vs. 150 milliseconds)
- How quickly it varies (e.g. changing once per second vs. changing several times a second)
- How it varies (e.g. changing smoothly vs. jumping randomly)
- How many delayed versions are added (e.g. one vs. several)
The combination of different options above can produce various sounds including:
- vibrato (the pitch varying up and down)
- wah-wah (that distinctive “Jimi Hendrix” or “Shaft” guitar effect)
- echo (a simple repeat of the sound a short while later)
- chorus (making one instrument sound like many)
- automatic double-tracking (making it sound like multiple recordings of a voice