Tbh, I didn't really follow the theme very much at all lol, but the repeating arpeggiating phrase came to mind after reading the prompt and the rest kinda just flowed from there. I also ended up taking about 3 hours on this, so it might not quite be in the spirit of Compost, but it's too late to fix that now :)
I might develop this into a full song later since I think it's got potential
Lyrics:
Remember this moment
Although we will soon go our own ways
Let’s keep our focus
On how we're together in this day
We've found our beauty
Because despite all that's happening
We're still making music
Nothing can take that away