Well, now, I feel inferior.
It sounds like it's made from a midi, possibly a mix of soundfonts. I can't tell which soundfont(s). What really gave it away was the seashore sound. I think this one would sound decent even on the synth that comes with Windows, though nowhere near as good as this.
(I like the music box! That sounds like something out of Threads of Fate with a Gauntlet 4-esque echo. My first thought when I heard the music box and the seashore was Transparent Shadow from the G4 soundtrack. ... I've tried making a midi of that song and it ... ah... did not sound anywhere near as good. I tried rolling the music box when I should have done something more like this.)

Check out the sound font topics--I think there's one that's still active, but there have been several, even recently.
I know nothing of Reaper or VSTs, other than that accessibility for these apparently involves extra work.
Not that I have room to talk, what with using Noteworthy Composer for all of my music composition.
Quick Windows Sequencer is a popular free and out-of-the-box-accessible midi sequencer. I find it confusing and tedious, and it likes to randomly transpose tracks when I try opening pre-existing midis in it. But I'm weird.

I use the bassmidi driver to expose soundfonts to Noteworthy and QWS, then Audacity to record the finished track.

So do you like, play on a keyboard or something for this to work? I'm curious, don't have any experience in this. If so, you're a darn good keyboardist.

I don't know how it works in Reaper, but NWC is more or less trying to be a word processor for sheet music. So you're writing it the way you would write music, which is kinda tedious because that involves lots of moving things to the right position on the staff and such. ... I should totally have contacted Noteworthy Software a long time ago and asked them about accessibility (either adding it themselves, or providing the necessary information to make Jaws or NVDA addons easily created).
Reaper's probably better, so it's probably not worth it now. So I'll just pretend I did this in 2002.