Early on, when I discovered the magic of the simple Pentatonic scale I figured the best way to impress anyone who was listening was to try to be the fastest guitarist on the planet. Which was impossible of course. But I learned a few licks that I could whip out when needed. And whip them out I did, way too often. You see, what I didn't realize was that speed in single note guitar playing is relative. If everything you play is fast, nothing sounds all that fast after a minute or so.
Before long I managed to learn the good ol' diatonic scale and while I immediately realized it didn't have much of a place in the blues stuff I was playing it sure could fill in the gaps when playing lead over songs that had more to them than the I - IV - V. Unfortunately, speed was still one of my main focuses and if you practice diatonic scales over and over and over trying to play them faster all the time, your leads will inevitably sound like nothing more than - scales, played fast!
Eventually I began to break out of that when I discovered modes and the importance of playing to the chord as well as the key. More on that in a minute.
Here is the most basic challenge of teaching someone how to improvise. I think the best analogy is learning how to read and write. The first step is learning the alphabet, and that's what scales are. There is one huge problem with that analogy though. There are limitless ways to put together words and in order to do it well, whatever it is we're writing on a piece of paper or via a computer keyboard has to happen, i.e. be visualized in our mind first. We visualize a word and then write it down. Not so with a guitar fretboard. Although we memorize a sequence of notes in a scale or a key the process is backwards compared to writing: inevitably, when learning to improvise we play a sequence of notes and a micro millisecond later, listen to what we played.
At some point in my journey in learning to improvise, that simple but important fact hit me squarely between the eyes (or ears!). What a great improviser plays happens in his or her mind first, then appears from the guitar via the fretboard and the playing hand.
Is that great lead player listening to what he's playing then? Well, of course!! But there is something way more complex going on. In that micro millisecond he confirms what his mind created and digests it, then decides if it is an idea that has merit. Should he expand on that idea, or move on? The challenge is to make these decisions instantly. That is the creative process.
As I said earlier, I began approaching my improvising not just from the perspective of the key but also thinking about chord tones to begin and end phrases on and also creating interesting sequences of notes by employing a more modal style of playing. I'm not going to delve into what that means from a technical standpoint right now. Suffice to say, understanding those concepts is one good reason to take guitar lessons! ;~)
You notice I just mentioned "phrases." And there was the other thing I began to learn. Another analogy for you. WhenWeTalkTheWordsDon'tComeOutAllAtTheSameSpeed. Some of our sentences are long, some are short. Sometimes we repeat for effect. This is vital when you're trying to come up with an interesting solo! Let the music breath. Don't feel like you need to fill up ever moment of time with sound. Listen to someone like B.B. King. He wrenches more emotion out of a few notes with plenty of space between his riffs than just about anyone else.
I still wasn't satisfied with my solos though (and I never will be - which is a good thing, I think). Something was missing. And you know what it was? Melody!
Back when I started playing lead guitar the idea was to play anything BUT the melody, assuming the song even had something recognizable as one. It was all about being immediately creative and yeah, playing fast, loud and high up the neck in many cases. Pretty cool for a little while but booooooring in the long run - and let me tell you, some of those runs were long.
I began listening to jazz players more and more and realized that when they improvised, I could often "hear" the melody even though they were playing something completely different. How could this be? I thought. It confounded me for a long time. Then I began playing with some very good jazzers and it became surprisingly obvious. They always started with the melody (or "head") and went from there. That way, phrases, intervals and melodic passages were established from the beginning; it gave them something to build on.
I began learning melodies of many jazz standards and you know what? All of a sudden, that process I mentioned earlier - making musical sequences in your head first, then playing them began to happen. Sure, I would rip off a fast line once in a while, hopefully if it made sense to do so, but I was learning to make my ideas compliment something tangible.
So this is what I try to do with my students when I teach the concepts of improvising. I give them the "alphabet" first - the scales, some arpeggios. But as soon as possible we begin concentrating on being melodic, whether in the form of an actual melody or a phrase that pre-planned. This way it has to happen upstairs first.
Learn the scales, learn the language but never forget that an interesting solo breathes. And don't try to fill every moment with sound. Spaces create anticipation of what will come next. Expand on musical ideas - a great way to make this happen is to try to play a simple phrase exactly the same way a few times, then add one or two notes, and repeat the process. It is way harder than it sounds, but you'll be making your guitar respond to your mind, not the other way around.