Ahmg, beautiful music, Paul. I've been trying to teach myself to make music as well, and uhh.. hasn't worked out so far.
Well, writing music is one thing. Time and experience and there are lots of sites online that can help.
...but full score orchestral compositions is quite a different thing. Not so many video tutorials on that!
That's where most of my learning goes these days.
But for example, the dungeon ambient one is based on something I wrote way back in the 90s using a mod tracker. I had my own MUD that I wrote with a custom telnet client that could do things like play music or in-built sound effects. That was one of the tracks I wrote for that... obviously fixed up quite a bit and some of the sillier parts removed.