One of the most useful guitar lessons I ever received was on how to switch from major pentatonic to minor pentatonic in a song. When I learned how to do this it opened up a whole range of new ideas for soloing on major-key songs.
I've created another Youtube jam track for switching scales specifically to help you to practice this technique. But before we get to that, let's explore this guitar lesson in full.
Scales to use on a major key song
If a song is in a major key, then of course you can use the major pentatonic scale. That is the natural scale to use being that it has the same notes as the underlying chords (albeit only five of them, which is why it's penta-tonic).
But you may have noticed that in rock, we often use the minor pentatonic scale to solo in a major key. Theoretically this should not work. The minor pentatonic scale has a minor 3rd, but the major key has a major 3rd. Those two notes do clash, but ever since the blues greats enjoyed smashing this dissonance together back in the early twentieth century, we've become so accustomed to it that it doesn't sound odd to our modern ears.
So with blues and rock and similar genres, when the song is in a major key, we have these scale options (among others):
Switch from one to the other
How to switch scales
On some level, you can switch from the major to the minor at any point and many guitar players do it. But it can take practice to make it sound like you intend to do it -- and that's the point. If it's not done carefully, the switch from one scale to another can sound like you're just hitting a wrong note.
The best way I have found to teach students how to switch is to get them to stay on the major pentatonic while the song is on the I chord (a C chord in the key of C), and then switch to the minor pentatonic when the song changes to the IV chord (F in the key of C).
This harmonic change lends itself really well to the major to minor switch and thousands of famous guitar players have been doing it for decades (listen to B.B. King).
So, how do we practice it? It's helpful to use a very simple jam track that has only two chords -- I and IV. This jam track I made also shows on the screen when you are switching chords so you'll know you're on the correct scale.
Play the major pentatonic on the I chord
Switch to minor pentatonic on the IV chord
Go back and forth until you can hear the changes and not have to look at the video for the chord info