I’ve seen some (but not all) electric guitars have what seems to be a small metal lever on their body. An example of this was the guitar that the guitarist from REM was playing at this years Glastonbury. He was playing his guitar, and then appeared to pull on this lever. I assume it alters the sound that is outputted by the guitar in some way? How does it alter it? What are the levers actually called?
I don’t know what they are called, but the levers change the tension of the strings.
The lever is known as a “whammy bar”, and is used to vary pitch by collectively tensioning or untensioning all strings at once. What it does is, using a large mechanical advantage, move the bridge (lower attachment point of the strings) very slightly.
I’m no guitar expert, but, I’ve seen it called a “whammy bar.” I believe that what it does is change the tension on the strings, thereby changing the frequency at which they vibrate.
Maybe you know this already, but when you pluck a string the frequency at which it vibrates (a.k.a. the frequency of the sound it produces) is determined by several factors, including: the composition of the string, the length of the string, and the tension on the string.
By changing the tension on the strings, the whammy bar changes the frequency of the sounds they produce. Since a whammy bar is a lever, you can rapidly alter the tension on the guitar strings, and create funny effects by moving the lever back and forth while the strings are vibrating.
The “whammy bar” is more formally known as the tremolo bar (or arm)…and less formally known as the wang bar.
Also, you’ll often notice in guitar shops that they’ve taken all the tremolo bars off the guitars on display; they don’t want kids going nuts with the things. You get your whammy bar after you buy the guitar.
As a guitarist I’m not really into the “dive bomb” howls and other noises that people get from the tremolo bar, but it’s still a great invention because it means that guitar is going stay in tune.
Ummm, have I been wooshed? I would think it would have the opposite effect.
The early tremelo bars (whammy bar, whatever you want to call them) were great for very quickly throwing a guitar completely out of tune. The el-cheapo ones you get today still do that. The more expensive ones are accompanied by a locking nut on the top of the neck. These do a much better job of keeping the guitar in tune. They are also a much bigger pain to tune up when the guitar does go out of tune, because you have to loosen the nuts, then tune the guitar, then tighten the nuts back up, then fine tune it again using the adjustments on the tremelo bridge since tightening the nuts throws it a bit out of tune as well.
Some tremolos are designed better than others. The good ones, like Floyd Rose are fully locking and some have little wheels to keep the strings from binding, helping to keep them in tune.
Darn, engineer_comp_geek beat me to the punch. I can’t believe it took me 5 minutes to compose that one liner.
I didn’t even think about the tremolo – I thought the OP was referring to the small lever (or switch) that is used to select the pickup.
Yep, you have the pickup selector which basically decides which pickup(s) (the device used to pick-up the sound) is used and the tremolo bar which when pushed on will lower the pitch allowing you to both acheive a tremolo effect and destroy your tuning.
Pete Townsend jammed his whammy bar through the webbing of his thumb & finger when I was at the Tacoma, WA. WHO concernt back in…what…1987? Dunno. It was their 25th anniversary tour.
He was doing that cool windmill thing with his arm and then all of a sudden he was ripping off his geetar and chucking it accross the stage…but then he left the concert. 
Tremolo bar is actually is misnomer. Tremolo is when a single note is played in rapid succession usually in 32nd or 64th notes. Vibrato bar is a better name for it since that describes what it does, change the pitch of the note/chord, though there is nothing wrong with whammy bar, etc.
Get a video of Eddie VH in his glory days, and he’ll use it a couple times a song. It slackens the strings, and makes the pitch lower, then higher as they tighten again.
Think long and hard before you get a guitar with a tremolo just because you think you may want to play Panama a few times. I’ve got a throwaway Ibanez with a Floyd Rose and to watch it in action just makes me cringe. It violates just about every aspect of luthiership where tone is concerned. Unless you play like Steve Vai then they’re only fun for the first two minutes - but you’ve sacrificed tone forever. Most of the guitarists I know who bought a guitar with a Floyd Rose (including myself) eventually ripped off the back and jammed a piece of maple into the tremolo cavity so that the bridge wouldn’t move.
Are you sure you saw a whammy bar? I always thought he just bent the neck (which would look like he was using a whammy bar because you place opposite pressure with the palm against the body). I remember the reason he hurt his hand once was because he windmilled on a borrowed guitar that had a whammy.
Don’t forget my telecaster’s B-Bender, which is a whammy bar for ONE string -
You pull the guitar down from the strap to activate this lever.
Mr. Daltry said that’s why he’d left.
Roger wouldn’t lie.
Roger is God.
He’s also Tommy.
So you were at that show? Weird coincidence.