The wah pedal creates a distinctive sound effect which is usually described as being vowel-like. This is basically done by altering parts of the frequency within the audio signal.
The wah pedal usage on bass
Most people associate the wah pedal with the electric guitar. Bassists however, have used wah pedals for years in both songs and solo performances. Just like the distortion/overdrive pedal, bass players began to plug into wah pedals which were intended for use with the electric guitar. The sound bassists got out of this experiment was actually pretty good. In fact, bass legends’ (like the late Cliff Burton of Metallica fame) use of the wah pedal have been well documented. Nowadays, wah pedals specifically engineered for bass are available and bassists can get the cool, signature wah sound while still keeping the low bass tones.
For those who aren’t already familiar with the wah pedal, it looks very different from “standard” effects pedals (like the pedal pictured on the “Effects Pedals for Bass” page). The wah pedal is usually much larger and more rectangular. The pedal is also used in a more manual fashion in that, you have to continously move a rocking treadle up and down with your foot in order to get the wah effect.
Available options to choose
There are also auto pedals available, which do come in the smaller “standard” form. As the name indicates, it is automatic and only needs to be turned off and on by stepping on it once. The advantage that an auto pedal has over a standard wah is that it responds and moves at a much faster rate, compared to a human manually moving a foot treadle up and down. It’s important to point out that auto pedals could also be marketed as and called envelope filter pedals.
When it comes to bass playing, the wah effect is great for bass-driven music like funk. Bass icon Flea, for instance, has used the wah effect on a few Red Hot Chili Peppers songs.
You may also be interested to read about bass synth pedal.