Have you ever wondered how guitarists made those really interesting "bendy" notes or wailed away? I used to play guitar when I was younger, and they had the same kind of things then. They were called "wah wah pedals"--at least affectionately. Now, though, the technology is far more advanced. You can do much more than just make bendy notes. You can make a whole new sound with "screamers." These really are just that. You can use a screamer to create all of the interesting sounds, and even adjust volume controls and other levels to get the perfect sound from your guitar.