I'm a pretty mediocre player myself, so take this with a large grain of salt. But...

There are no right notes when playing lead guitar. Unless you're doing jazz, lead guitar is more about feel than playing the "right" notes.

The simplest approach is often the most effective one. Pentatonic scales are God's gift to guitar players. An easy way to think about pentatonic playing is to think of a pentatonic scale as a major scale (say, C Major):

C D E F G A B C

with any possible "clashing" notes removed. Specifically, there's half-step clash between the E and F and the B and C. To "fix" this problem, one of the two clashing notes are removed from the scale. With the E and F, the F is removed, because the E is more important (it's a member of the C Major chord). With the B and C, the B is removed (the C is also a member of the C Major scale, and the main note of the scale). That leaves a "gapped" scale with no half step clashes:

C D E (gap) G A (gap) C

The really cool thing is that every note of this scale is going to sound good over any of the triads in the scale of C Major, because you've gotten rid of the half-step dissonances. Some notes will sound better than others (depending on context), but you don't have to worry about hitting a "wrong" note. So you can wail over the chord changes and concentrate on the feel of the solo.

Pentatonic scales are great on the guitar, for a number of reasons:
  • There are only 5 notes, so there are 5 different patterns (each starting on a different degree of the scale), so they are easy to learn.
  • Each of the different shapes corresponds to an "open" guitar chord shape, so that helps make then easy to memorize.
  • The scales are easy to play, because they work out to an easy fingering of two notes per string.
  • Since these are two note per string scales, the "bottom" notes of one scale form the "top" notes of the next scale. These shape are easy to memorize.
Google for the "CAGED" system (called that because of the notes in the C Major pentatonic scale) and you should be able to find lots of information.

If you check out the circle of fifths, you'll note that on the "flat" side of C Major is F Major, and on the "sharp" side is G Major. (These are also the IV and V chords of C Major).

The F Major scale differs only from the C Major scale by a single note - Bb instead of B. The scale G Major also only differs from the C Major by a single note - F# instead of F. Note that these notes are conveniently the same two notes dropped from the pentatonic major scale:


F Major Pentatonic: F G A C D F F = IV chord in C Major
C Major Pentatonic: C D E G A C C = I chord in C Major
G Major Pentatonic: G A B D E G G = V chord in C Major

Notice that they're all diatonic to C Major!

That is, the notes in the pentatonic scale are common to the major scales to the immediate left and right on the circle of fifths, which (conveniently) happen to be the IV and V chords.

More simply said: you can play the pentatonic scales of the IV and V chords, and they'll be diatonic to the I chord's major scale.

Even more simply said: you can't play a wrong note using these scales, either.

So if you get bored playing the same C Major pentatonic scale over the changes, you can also play the appropriate pentatonic scale over the major chords, and not have to worry about playing a wrong note: the notes will match the chords, as well as being diatonic.

For example, if in C Major the chord changes to F Major, then use the F Major pentatonic scale instead. Or use is with the C Major pentatonic scale. They both have the same "shape" on the guitar, they just start in different positions.

And if, in C Major, the chord changes to G Major, you can choose to use the G Major pentatonic scale instead of the C Major pentatonic scale. Again, you're guaranteed that you won't hit a "wrong" note.

You can play the relative major scales over the minor chords. That is, C Major pentatonic over Am, F Major pentatonic over Dm and G Major pentatonic over Em. These are "relative minors" of the major scales, and they fit hand in glove.

Or you can just stick with playing the C Major pentatonic over everything (assuming you're in C Major), and it'll all sound good.

That's good for country music, which uses a major tonality. But what about rock and blues?

The good news is that pentatonic scales work great there, too!

For blues, you can use the same shapes but shifted up three frets. For example, if you're playing a chord progression in the key of E, instead of playing an E Major pentatonic scale over it, play an E minor pentatonic scale.

E minor is the relative minor of G Major. And in the same way that the G Major scale has the same notes as the E minor scale:

G Major: G A B C D E F# G
E minor: E F# G A B C D E

the G Major pentatonic scale has the same notes in as the E minor pentatonic scale:

G Major pentatonic: G A B D E G
E minor pentatonic: E G A B D E

Equally conveniently, you can play the E minor pentatonic scale by shifting the E Major pentatonic scale three frets up. Same shape, different sound. Congratulations - you're now playing the "blues scale" over the changes.

And since you're using a pentatonic scale, you can't hit a wrong note.

Well, although a lot of people call this minor pentatonic scale the "blues scale", it really isn't. It's more the "rock" scale, because it's used so much in rock solos.

The "real" blues scale is a hexatonic (6 note) scale, not pentatonic (5 notes). It adds a raised fourth to the scale. But I think it's easiest to think of it as a pentatonic minor scale with an added scale degree.

You'll find the pentatonic minor scales are often referred to as "blues boxes", with the G Major pentatonic shape being the workhorse for many, many rock solos, often only adding a few notes from the E Major pentatonic scale that sits on top of that.

There's one other point that I should mention, and you've touched on them: using "guide tones" in your solo. It's basically Schenkerian Analysis in reverse. The core idea is that you can break down a melodic line into "important" and "less important" notes. As you "strip away" the "less important" notes, you're left with the "primary" melodic line.

You can do this in reverse when you build your solo, by selecting chordal notes (typically the 3rd or 7th of the scale, since they're harmonically important) as the "main" tones to "guide" the direction of your melody. This helps give your solo focus by keeping it harmonically grounded, and from wandering aimlessly.

But I'd really concentrate on using pentatonic scales. It takes the focus off playing the "right" note, and gets you working on the feel of the solo, which is where the expressiveness and soul of the solo lies. Guitar solos aren't about which note you choose, but how you play it.

Did that make sense?