The history of the Wah-wah pedal is an interesting thing. Although we commonly associate wah-wah with people like Jimi Hendrix, it's actually been around since the 1920s when trumpet and trombone players were doing it manually by moving a mute in the instrument's bell. It wasn't until 1966 that a wah-wah pedal was made to stimulate the effect for guitarists.

Adding wah can really change the vibe of the song. Can you imagine hearing Jimi play the song above without using a wah-wah pedal? Sure, but it just  wouldn't sound as good would it? Many guitar players love to incorporate some wah action into their sound, but how many of them actually know how it works? Not that it's a requirement for using it, but it is pretty cool to know what's happening to the sound frequencies when you're using a wah-wah pedal. Check out this article from Slate.com which breaks it down on a scientific level. 

Then if you're in the need for some more wah inspiration, check out this discussion about the best wah-wah songs on GuitarZone.com!