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Auto-Wah

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Often followed by + Gain + Limiter

A wah pedal is a resonant filter with a foot on its frequency. An auto-wah replaces the foot with an envelope follower, so the filter position tracks how loud the signal is at that moment.

Sensitivity

Sensitivity scales how far the envelope pushes the filter, from 0 to 100%. The follower measures the level between -48 dBFS and 0 dBFS, and sensitivity decides how much of that range reaches the sweep.

Quiet recordings need more of it. If the effect only opens on the loudest hits, raise sensitivity rather than the sweep range.

Base frequency and sweep range

Base frequency is where the filter sits when nothing is playing, from 80 Hz to 1.5 kHz. Sweep range is how far up it travels at full envelope, from 0 to 4 octaves.

A base of 250 Hz with a 3 octave range covers 250 Hz to 2 kHz, which is the vocal-sounding sweep most people expect. Bass parts usually want a lower base, around 120 Hz, so the filter does not remove the fundamental of every note.

Resonance

Resonance is the Q of the band-pass, from 1 to 12. The output is scaled by the inverse of Q, so raising it narrows the peak instead of making the effect louder.

Low values sound like a tone control moving. Values above 6 give the vowel-like character the effect is known for and start to ring on sustained notes.

Release

Release sets how long the filter takes to close, from 30 to 600 ms. The attack is fixed at 5 ms so the filter is already open by the time a note is audible.

Short release times give a percussive quack per note. Long ones ride across a phrase and follow the shape of the part rather than the individual notes.

Mix

Mix blends the filtered signal against the original. Because a band-pass removes everything outside its peak, mixing some dry signal back in is often what keeps the low end and the air in place while the sweep sits on top.

Example: a funk bass line

Sensitivity 75%, base 140 Hz, range 2.5 octaves, resonance 6, release 120 ms, mix 80%.

Each note opens the filter on its attack and closes before the next one, and the 20% dry signal keeps the fundamental audible through the sweep.

Frequently Asked Questions

It opens a resonant filter as the signal gets louder and closes it again as the signal decays, so each note is played through its own filter sweep. It reads WAV, MP3, M4A, AAC, Ogg, Opus, FLAC, AIFF, and WebM audio, and exports in the format the source arrived in.

They are the same idea and the names are used interchangeably. Both drive a filter from an envelope follower rather than from a pedal, which is why the effect follows how hard a note is played.

Either the sensitivity is too low for the level of the file, or the sweep range is at 0 octaves. Raise sensitivity first. A quiet recording never reaches the top of the envelope range, so it never opens the filter fully.

The release is too short, so the filter closes between notes and reopens on the next one. Raising the release to 200 ms or more holds the sweep across a phrase.

Yes, though the envelope then follows whatever is loudest. On a drum loop the filter opens on each kick, which is the classic funk sound. On a full mix it usually works better at a lower mix setting, around 40 to 60%.

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