Bending strings refers to stretching them with the left hand to increase their pitch, gradually or instantly. When bending a string, the string is still contacting the fret, but the string is being pushed either up(towards the ceiling), or pulled down(towards the ground). This results in the stretching of the string, bringing greater tension, and raising the pitch. Bending strings can be a useful way of adding variety and style to your playing. When bends are gradual, they are akin to the sound of a saxophone, or other instruments that make use of 'sweeping' from pitch to pitch. An example of an instrument that does NOT bend notes is one like the piano. There is no way of getting all the pitches between any two consecutive semitones.
By bending a string, we can achieve any pitch we want, including quarter tones and other sub-semitones. The more we bend a note, the higher the pitch becomes. On an electric guitar, it is possible to bend strings so that they will sound 2 whole tones(or more) higher than the note of the original fret. On an acoustic guitar, it is harder to bend the strings, and bends of 2 whole tones on acoustic guitars are not common.
The first bends that will be discussed are the bending of notes on the top three strings(E B G). When bending these notes, the string being bent should be pushed up(towards the ceiling). For example, if we took the note on the 10th fret(A), sounded it, then pushed it up towards the ceiling, the pitch would raise. If we pushed it up enough, we could get it to sound like the note on the 12th fret(B). This means that you have just bent the string up 1 tone.
Since bending allows to play any pitch(even the ones in-between semitones), it will take practice to make a bend sound like we want it to. You might bend the note to much, and then the resulting note will note be an exact whole tone higher, it might be 1 and a quarter tones higher. The only thing you can do about this is to practice bending, and after a while, you'll start to get a feel for how much you have to bend a note to obtain a certain pitch.
Getting back to what we said before, the top three strings should be usually pushed towards the ceiling when being bent. If we tried to pull them down, sometimes we would pull them right off the fretboard, and we'd get a funny sound. On the other hand, the bottom three strings are usually pulled down when they're being bent. The reason for this is that if we pushed some of these strings up, they would also go right off the fretboard. So:
E push up
B push up
G push up
D pull down
A pull down
E pull down
These rules are not written in stone. If, for example, you wanted to bend a note on the G string just a little, nothing is stopping you from pulling on it. Just as long as you get the sound you want, and just as long as the string doesn't go off the fretboard(unless that's what you want).
Bending strings requires strong fingers, especially if you're using an acoustic guitar. Don't expect to be able to bend a note a tone on your first try, unless you have strong fingers. There are some things you can do to help you in bending notes. When bending notes by pushing up, there's nothing that says you must only use one finger. What you can do is place your pinkie on the fret that you want to bend, and then place one or more of your other fingers right behind your pinkie, on the same string. Now push up with all your fingers. Isn't that easier? It gives you better control also. When pulling strings down, you can do the same thing, although it's not as effective.
Now we will discuss some things that you can do with bends. The first is just the regular bend. When doing this, you'll sound the note before bending it, and then while the note is still ringing, you'll bend the note to raise the pitch to whatever you want. This is useful if you want to accentuate a certain note. For example, if you're target was E, you would place a D note, and then bend it up to an E note.
Another is the 'gradual' bend. This is the same as the regular bend, except you can take extra time in the actual bending of the note. This is most effective when using an electric guitar with some kind of distortion or other effect to make the note sustain. If you're using an acoustic, or the note doesn't sustain long enough, the note will have died out by the time you finish bending it.
The 'bend and release' is when you bend a note, and then 'unbend' the note so that it goes back to it's original pitch. For example, you could play an A, then bend it to B, then release the bend so that the pitch will lower again to A. In this way, you've actually played three notes. It's sometimes an interesting alternative to just playing a simple A, B, A. By using bends, even though you're getting the same notes, you're getting the stuff in-between them while moving to each of them through the bends. It gives a totally different effect.
The 'prebend' is when you don't sound the note until you've actually bent it. For example, you would place your fingers on the 10 fret, but you wouldn't sound it. You'd then bend it with out making a noise, and then you'd sound the string. You might wonder what the use of this is, because you could get the same thing by just sounding the fret that corresponds to the pitch you want, instead of prebending a note underneath. You'll see why it's useful in the next kind of bend.
The 'reverse bend' is a combination of a 'prebend' and a 'bend and release'. What you do is prebend a certain note, sound it, and then release it to whatever the original pitch would have been. For example, you could prebend the C note(but you wouldn't actually hear the C note right away), so that when you sound it you here a D. Then you would release the bend, and what you'd get is a bend going from D to C. That's why it's called a reverse bend. It gives a neat effect.
Of course, you can take these suggestions and put them together in any combination you want, and make your own uses for bends. Just remember that bends are an important part of guitar playing, especially if you are playing a blues lead line on an electric guitar. Things to remember from this lesson:
1. Bending a note refers to stretching the string(either up or down) so that the pitch is raised.
2. In this way we can get all the pitches between semitones. We can also create a 'swooping' effect between two notes, such as on a saxophone or whatever.
3. The top three strings are generally bent by pushing them towards the ceiling. The bottom three strings are bent generally by pulling them towards the ground.
4. You don't just have to use one finger for a bend, you can use your other fingers to support the finger you are using to bend.
5. There are a number of things you can do with bends, such as the 'bend and release', the 'prebend', and the 'reverse bend'.
6. There are a lot of other things that you can do with bends that haven't been discussed here.