It is absolutely imperative if you want to be a great guitar player, to learn how to play across the entire fretboard, both in playing solo and lead lines and in playing chords, inversions, and upper partials. Most scales and/or modes are played in a minimum of five positions. In each position, the root note or tonal center note is located in a different place on a different string, and the fingering pattern for each position is unique to that position. A lot of solo and lead line playing gravitates toward the top three strings in the higher registers of the guitar, and as you look at each position you have different notes at the top for each one, emphasizing different intervals and different sounds. Therefore, you get different sounds from phrase shapes you might create in each position. It’s because of this variety that it’s important to be able to solo in all positions in order to access the complete palette of sounds and relationships.
A similar thing happens in the domain of chord playing. Each inversion has a different element of the triad in the top voice, and so there is a different stacking of the triad notes and therefore there is a different sound even though it is the same chord. Learning to maximize your playing by learning all the inversions and partials will allow you to have greater flow in your voice leading as you change between chords. You can gain enough control to create harmonic sections that imitate string parts, horn parts, and more.
It is not enough for you to know that you need to learn all your scale positions and all your inversions, you need to learn them. And I don’t mean learn them intellectually, but in the core of your musical awareness and deep into your muscle memory. It is important that as you think and feel the part you want to play, the ability to render the idea on the guitar is effortless and fluid and connected to your emotions.
Just to let you know how strongly I feel about this, I want to tell you a little story that involves a lesson with a top student. This student was making remarkable progress and was fluidly playing throughout his chosen scales and modes, making interesting and dynamic phrases and blossoming into a very good player. The only problem for me was that he wouldn’t leave the root position of the scale (I believe that it was the Dorian mode.) He didn’t understand that while his playing was getting really good, that after about the third or fourth song his solos started to sound the same, because he had boxed himself in with regards to covering the full range of the fretboard. No matter how hard I pushed for him to play in the other positions, he just wouldn’t do it and insisted on staying where he was comfortable and knew what he was doing. After a mental wrestling match that lasted about four weeks, I took his guitar and wrapped the neck with duct tape over the position on the guitar that he was accustomed to playing in, and I forced him to begin to play in the other positions.
He left that lesson really angry with me, but I also believe that he had gotten more out of it than he would admit, because within two short weeks he was playing beautifully all over the guitar in all positions and with great new insights into phrasing combinations that had been unavailable in his previously limited approach. This student went on to play professionally with great chops and a great “feel” for the instrument. Sometimes a guitar teacher has to push and doesn’t get to be Mr. Nice Guy, but I would argue that the results are usually worth it, especially when a student gets the message and goes on to realize his potential.