Wow, a long review for just a loop. :O
But it's a GOOD loop. Classical-sounding, and your composing skills really shine here. :D I have to say, great instrument choice, and the melody's great, too.
It's played by... what, a woodwind? I don't think it's an oboe, though... enlighten me on what it is, will you? XD But great instrument choice, very fitting.
I have to point this out - your title, Up and Down, is SO fitting. :D What your strings play at times, UP and DOWN. UP and DOWN. UP and DOWN. UP and DOWN. Etc, etc. Very well-composed and a creative element.
Enough flattery, as much of it as I have for this song, though I suppose you did deserve to know what you did right, for future songs, right? :P But you did pretty much everything right in this song, VERY creative, (can't stress that enough) etc... except for what I'm about to criticize you on.
The only criticism I have for this song is how it ends - yeah, I know it's a loop, but it seems to end on an odd measure - not the 16th of 16, the 8th of 8, or even the 4th of 4. It ends suddenly. I think you cut it at the wrong point... you either should have kept going, or started it at a different point and ended it at a different one. What I'd have done would be to take the first four measures, and put them at the end of the song... that would have made more sense to me. :P
Wow, a long review for such a short song... hey, you deserve it, you're good at this. Keep up the good work. :)