Anything goes in the world of music composition. Many artists play solely by ear by piecing ideas together through trial and error. But there are fundamental concepts that underlie all music like scales, chords, progressions, modes, etc.
If a song doesn’t all fit into one key, then it’s a combination of different keys. Sometimes this is thought of as borrowing elements from other keys. In this case, you have to break the song down and separate it into pieces that each fit into a key.
Another possibility in this type of situation is the usage of scales beyond the pentatonic and major scale patterns I teach. For example, the harmonic minor and melodic minor scale. But you need to understand pentatonic and major scale theory first as advanced concepts stem from them.
Going through this trouble to understand a song’s construction is not usually necessary in styles that don’t require much melody or harmony. For example, some heavy metal riffs are simply based on chromatic movement or rhythmic noise. It can be kinda pointless to try and connect these things to some sort of structured guitar theory.
To learn more about music theory for guitar, including scales, chords, progressions, modes, and more, sign up for a free preview of my Fretboard Theory books and DVDs by using the form on this web page.
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Mr. Desi Serna
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