I’m currently spending some time studying, “Composing Music,” by William Russo. It’s a book I bought several years ago but never finished. I actually wanted to major in music composition, but ended up majoring in percussion instead. Guess I’m trying to kind of make up for some of the knowledge that I feel I may be missing.
The chapter I’m studying right now is on counterpoint, the technique of writing two melodies that are sounded at the same time. This technique was used a lot in the guitar playing of the group Boston, one of my favorite bands.
Some of the exercises in the book have me writing with 2 scales at once, for instance, E Phrygian in the treble clef, and C Lixian in the bass clef, resulting in bitonality. You actually hear the music in two different keys.