Whammy Bar
The whammy bar can be used to drop (and raise on some bridges) the pitch of all 6 strings. It differs from bending in that it typically allows dropping instead of or in addition to raising pitch, greater size in pitch changes, affecting multiple strings simultaneously, and shifting pitch more quickly. It can be used for a number of special techniques to enhance one's playing.
Contents
PreReqs
Notation
The whammy bar is very difficult to represent in tab. I recommend doing so exclusively above or below tab. However, you may see things like this:
--5---\1/--\1.5/------5---/1\--/1.5\--
This initially looks like a slide down to the first fret, but you can see that it's followed by an upward slide to nothing. This actually represents a quick whole step dip by pushing the bar downwards. So in the above example, you'd pick the 5th fret note, dip a whole step then whole+half step, pick the note again, then pull up on the bar to raise the pitch a whole then whole+half step.
For tab that heavily uses the whammy bar, it's common to see s used in place of / and \ to indicate slides. Then all /s and \s indicate whammy bar dips or rises.
Techniques
Dive-Bomb
The classic whammy bar technique is called a dive-bomb. It involves simply pressing the bar down further and further until the strings becomes slack. Any notes that were sustaining when the dive-bomb begins will drop further and further in pitch until they turn into low frequency noise.
E--0-VVVVVVVVVVV--\---24---/--
This technique is simple: just keep pushing on the bar! The only thing to watch out for is that open strings will start ringing as you add more slack. I like to mute those strings with my left-hand before starting the dive. However, in some cases, that open-string ringing may be a desirable part of the effect, especially once the strings are completely slacked.
Slide to Nowhere
This technique uses contrary motion by sliding up the frets on one or more strings as you push down on the whammy bar. The trick is to time them so that they are increasing and decreasing the pitch at the same rate, so that it doesn't sound like the pitch is changing. Once you've gone pretty far (~7 frets), you can reverse directions by sliding down while decreasing pressure on the bar to continue the effect. Or you can release the bar quickly, so the pitch rises very quickly, like you stored all the energy from the slide and are releasing it all at once.
Vibrato
The whammy bar makes an excellent means to get vibrato. It's probably the best or only way to do so for chords and the least noisy way to do so for notes that are sustaining until they completely decay. It's also helpful to apply vibrato while sustaining a bend, in order to hold the bend at the target pitch. See Vibrato.
* use whammy bar B--17b19----~~vvvvvvvvvvvvvvvv--
Eastern Instruments
One of the characteristic sounds of Eastern stringed instruments is the the downward pitch shift during the attack of a note. This can be simulated by pulling up on the whammy bar while picking a note but instantly releasing the bar. It may not be necessary to pick the string, but instead use a hammer-on, or pull-off/slide from an existing note. Sliding down into a note while using this technique can take it a step further.
* pick/hammer note during whammy pull G--(5)/1\----(6)/1\----(9)/1\----(10)/1\--
Synth
A common way to embellish a synth sound is to pitch shift upwards, into the note. This can be simulated with bending, but often bending is too slow and limited in pitch to mimic some of the more noticeable synth effects. So instead we use the whammy bar, depressing it before plucking the desired note, then quickly releasing it afterward/during. With the strings slacked by depressing the bar, it's often unnecessary to pick the string at all - a hammer-on works just as well, freeing your right hand to focus exclusively on timing the bar.
Flutter
On a floating bridge, one performs a flutter by quickly hitting/pushing the bar and sliding off of it, causing the bridge to snap back towards its resting position. Because the floating bridge relies purely on counter-balancing tensions to find its resting point, the momentum of the snap-back carries it past neutral position, where it then changes directions. It flutters around the neutral point before returning to rest. It's basically like a super-fast, diminishing vibrato.
To get a feel for the technique, position the bar so it is pointing towards the nut. Push the bar down with your ring and pinky fingers from your picking hand to lower the pitch of all the strings but don't wrap your fingers around and grip the bar. Now move your entire right hand towards the nut while maintainting pressure against the bar - your fingers will start to slide towards the end of the bar. Keep moving your hand, allowing your fingers to slide off the tip of the bar. With nothing to maintain pressure, the bar pops back towards neutral, but flutters before getting there.
One can perform a flutter by using the bar initially in either direction. In other words, you can point the bar towards the back strap pin or the opposite direction of the nut. Now if you push on the bar, it will raise the pitch of the strings. But if you slide-off and let it snap back to neutral, it will still flutter the same as when done the opposite direction.
Most flutters are done while the note is sustaining, almost like a secondary accent. For example, if the same note is played consecutively on the 1 and 2 beat of a measure, the performer may pluck the first beat then use a flutter on the 2nd beat.
Fast or Large Bends/Wobbles
Bending is often done to get up to a certain note. A bend's speed may be particularly fast, but it is usually intentionally a little slow. The transition between notes is thus emphasized. Most bends are only a half step or whole step. Larger bends are often used by some musicians, but they are generally more difficult.
Using the bar to bend can be used to break down these limits. It can change pitch very quickly and in large-distances. And it can lower as well as raise pitch. It has a slightly different sound than bending, so it could also be used for slight variation.
The bar allows shifting above/below a sustained note's pitch and returning the original note very, very quickly. You just tap or yank on the bar real quick. A bunch of those done in succession is what I call a wobble.
Screaming Squeals
A technique made popular by Joe Satriani and Dimebag Darrell is the screaming squeal. This involves pushing the bar down hard while keeping all the strings muted. The strings should basically be almost slacked. Pluck the string you want to sound, usually the G or B string. Quickly tap a natural harmonic (I like to use the 5th fret, 4th order harmonic). And slowly release pressure on the bar so the pitch raises. You should get about an octave of pitch shift as you let up the bar. So you get a squealing, high-pitched sound that keeps getting higher and higher pitched. Once the bar reaches neutral, you can keep going by pulling up on the bar, going even higher.
Huge Vibrato/Horsie Sounds
If you've tried to use the bar for vibrato, you'll notice it's a lot easier to make the vibrato awkwardly too wide than sweet and subtle. Here we just go nuts and purposefully for the widest vibrato possible. This is for an out-of-control, chaotic sound.
If performed on a higher note or interval, this can get a horse-type sound, especially if you are reverse bending or using increasing bar pressure so that the overall pitch direction is decreasing.
Tuning Issues
Extensive use of the whammy bar can cause all the strings to go out of tune, particularly on a floating bridge. It's best to save such for the end of a song or before a set break, where you can either retune the guitar or switch to an in-tune guitar.
Many claim one of the flaws of a floating bridge is that your double-stops are out-of-tune. This means that if you are bending on one string but not another, the bend increases overall string tension on the bridge, causing it to pull-up a little, which causes the unbent string to fall a little flat. There are two simple solutions: pull up on the bar a little or apply a slight bend to the flatted notes. This counteracts the raised bridge and keeps the unbent note in tune.
There are devices that claim they can help keep your tremelo bridge in tune even with whammy use. They use a double-springed hinge similar to a bar mini-door that can open in either direction. These work to various degrees, but they all tend to diminish the desirable qualities of the floating bridge by preventing a smooth transition between pitching downwards vs. upwards. They particularly hurt flutters, but also affect vibrato. I recommend not using these.
Ultimately, your tuning stability is a byproduct of the quality of your guitar's parts and setup. The big things to look at are the bridge's knife edges and your bridge posts. If either of these are heavily worn, they will not settle to "neutral" consistently. Also the knife edges should be perfectly perpendicular to the posts in neutral position. If the bridge is angled differently, you will need to adjust the tension of the bear claw springs accordingly.