Try the interactive tutorial, or download the Sheet music here: https://musescore.com/user/31319606/s...
Writing this down for myself:
I wanted a picnic theme, for a celeste mod I'm making. I originally picked out 2 strings (1 pizz, 1 arco), a piano, a guitar, glock, and some percussion. I modeled it after a youtube video I watched some time ago about how switching keys down the circle of 5ths can sound like a dramatic movie, so I took that into account. To further that style, I used big open 9th chords like in Studio Ghibli.
The intro I just did some fancy chords, I think they're 5ths apart I don't remember too well. But then I went for a simple I-II-I-vi, then modulated to F minor, which I love how it sounds. A little too melancholy for this theme if I'm being honest but I love it regardless. Then I made the best modulation ever back into C major, with voice leading! Ebmaj-Cmaj, resolving down a m3 to a major chord. Remember that! With good voice leading that sounds like heaven. Then I went off and just noodled around, I-bVI-iii-IV (can you tell I like the 4 chord), and repeated. Then I thought it was too short to I extended it with a little phrase that also has a modulation. I used secondary dominants, I-V/ii (or VI)-ii-V-I a perfect cadence, to set up a transition into the parallel minor key. Then I did some minor key stuff I don't feel like explaining. The end!