A key idea in this piece relates to what is traditionally known as the minor plagal cadence. Am to EM is the minor plagal cadence in the key of E major. That is, iv I, using Roman numerals, in any major key.
I have a separate page explaining the conventions I use for writing and discussing music. The guitar score follows this analysis.
With the standard plagal cadence, which is IV I, for example AM to EM in E major, there is more than one voice leading option for the major third of IV, whereas in the minor plagal cadence, the minor third of iv usually resolves to the perfect fifth of I. This is an example of traditional chromaticism. For example, Am to EM in E major, with C B in one of the voices.
Sometimes, a three chord version was used, IV iv I, harmonising a three note downward chromatic run, for example, the melody of C♯ C B played against AM Am EM in E Major. I'm not sure if it has a standard name, but I'll call it the major minor plagal cadence (mmpc). This was one of the earlier steps in the transition from Classicism to Romanticism, the latter employing more and more rolling chromaticism as that period progressed.
Lot's of bands were using it in the sixties and seventies: Pink Floyd, Led Zeppelin et al. When I started writing this piece, working with guitar, which was the only instrument I used for composing back then, it began with investigating a theme, which was EM EM sus 6 E7 sus 2 and I was looking for a way to continue it. I eventually decided on the mmpc.
A third idea, was a pedal bass jumping from the open low E string to its octave at the seventh fret of the A string. So, three ideas came together in what became the opening theme, to start me feeling like I was coming up with a new composition. Neither of these ideas was particularly new, but I was putting them together in my own way and wanted to use the mmpc as a motive to develop further sections to come up with a much more involved composition. I did not just want to write another pop song. This arrangement is 2 minutes and ten seconds long, a short piece, but there's a lot of work in it.
Having settled on the opening theme (A), over the pedal bass, which is bars 1 and 2 repeated once. Note that it does not have its own cadence and it ends wanting to go somewhere, so it neatly drops onto the EM at the start of the repeat. Here it is a classical mmpc, AM Am EM, with the melody C♯ C B, which is sixth, flattened sixth and fifth. Then I started looking for ways to develop the mmpc.