- Controls the frequency range in which the filter moves.
- Bass Switch
- Lets low sounds through when it is down, and is especially useful when playing bass guitar or bottom string notes on lead guitar.
No forum threads about this effect yet.
- Electro-Harmonix Doctor Q Envelope Follower
- Electro-Harmonix Nano Doctor Q - Envelope Follower (Nano series)
- Ishibashi Triangle Env (Japanese copy?)
- Jack Orman's Dr. Quack (DIY project based on the Doctor Q)