Just wanted to make sure I understood how things worked before diving into it too deeply.

So I understand the idea behind the pattern editor, I've used it to make short sound clips and stuff (and then these are obviously arranged within the music editor to make different instrument tracks, etc)

From what I can tell at a surface glance though, is that the music editor only supports one song. Is that correct? I get the impression that I can set the loop start/end points to choose between different pattern sets to allow for multiple songs (eg 0-7 might be song 1, 8-16 could be song 2, etc). Additionally, I assume that I can create my own pattern arrangements on the fly by means of poke()

Anyone know for sure?

That's all correct, yes. music(n) starts playback at the nth music pattern, and the patterns include looping instructions (proceed to next, go back to closest loop start, stop).

Music pattern memory is described here: http://pico-8.wikia.com/wiki/Memory#Music