If you're like most guitarists, you've familiarized yourself with the guitar fingerboard by learning the notes "in position". You would then play scales and their variations across the neck without having to move your fretting hand. Eventually, you would be able to connect these positions and cover most of the ground on the fretboard. Many guitar teachers approach learning the neck in this way. First, you learn the notes in open position, then third (first finger at the third fret), then fifth, seventh, etc. It's the way I was taught and for a long time, I thought this was a thorough method of learning the neck. However, I began to realize that playing horizontally was only half of the picture.
Seeing the neck vertically was a great revelation for me—it got me away from patterns that I had learned through "muscle memory" (favorite patterns that all instrumentalists rely on, only because they've practiced them a zillion times). Granted, you can start to develop habit patterns while playing vertically as well, but since your hand is constantly moving all over the place, the patterns don't stick as easily. It's as though you are playing two different instruments—the horizontal guitar and the vertical guitar. In fact, some guitarists have described playing vertically as having six distinct instruments at your disposal.
Let's take a look at some exercises in vertical playing:
We'll start by playing the F major scale up and down the high E string. The fingering doesn't matter much. Try it with only your first finger. Try it with the first and second finger. Try it with your sixth finger. Anything goes.
Notice that you get a really good feel for the half and whole-step intervals in the scale. Now, don't cheat yourself. Play the scale up to the highest fret possible and back down again (a little more than an octave and a half). This is how you'll get to really know the fingerboard.
Now do it in the key of C, starting on the 8th fret. You practice in all twelve keys, don't you? No? Why not start now? (I like to practice using the cycle of fourths: C,F,Bb,Eb,Ab,Db,Gb,B,E,A,D,G. You can use any movement you like, as long as it covers all twelve keys.) See the diagram below:
Notice that we started on the 8th fret, went all the way up to the next C, and came back down, passing the starting point and then back up to finish where we started.
Let's go a step further and use some melodic patterns. This would probably work best using the first, second and fourth fingers. We'll use the F major scale on the high E string:
How did that feel? Liberating? Made your brain hurt? Good. You're doing it right. Don't forget to use every fret available. Here it is in the key of Bb:
I don't want to alarm you, but there are five other strings to practice on. That's a lot of work!
The next logical step is to use two adjacent strings. Let's try the high E and B strings in the key of C. I have a new pattern for you as well:
Are you getting the feel for it? Good. You should begin seeing things in a whole new light now.
If your brain isn't already leaking out of your ears, let me give you some of the variations in practicing this way:
Play an infinite number of patterns up and down each of six strings.
Do the same with different scales.
Do the above in all twelve keys.
Do the above and use only the first two strings together.
Only use the first and third strings.
Only use the first and fourth strings.
Only use the first and fifth strings.
Only use one finger.
Only use two fingers.
Only use three fingers.
Use the first, third and sixth strings.
Use the first, third and fifth strings.
Use the bfneislkf ; kdpwoi fjewief as*&^%^%*^$)Ahhhhhhhh!!!!!!!
You get the point. It's a ton of material to learn, but don't let it overwhelm you. Just take it a little at a time—maybe ten to fifteen minutes per session. You'll start to feel comfortable with it and you won't be able to remember what it was like to play only your horizontal guitar.
For further exploration on this and other topics, check out The Advancing Guitarist by Mick Goodrick (Hal Leonard Publishing). This book alone could occupy the rest of your musical life. So, what are you doing just sitting there? Go practice!