Instruments.
The piano at its loudest is a bit fuzzy. The rest isn't bad, BUT, I thought I might quote you here, from the audio ad thread: "A simple piece to chill to."
I think you can bring out that chilled feeling more by doing a couple of small things. Add some very soft strings in the bass, and maybe kick the brass up an octave (it might still sound ok as it is though, I'm just trying to piece it together), tone down the brass a bit, maybe use a brass sample that isn't so punchy, the initial moment when the brass first plays is very loud and short, and a softer brass sound sustains. If you can, try and get the brass to be softer, the same volume at the start, or maybe find a brass that increases in, so that the first beat is a lot quieter, and the brass is a lot more soothing.
I think those should bring this piece to a new level, but it was still pretty good work as it is.
Cheers.
WB