I listened to this just on a whim but boy am I glad I did. First thing I wanna say is that the composition and phrasing in this is absolutely brilliant. I was enraptured through the entire song. Your harmonies are genius as well, absolutely fantastic work.
I do have some issues with the way this ended up in the production department though, it's gonna seem like I'm really dumping on you in this review but it's only because I really really liked this piece and it comes from a genuine place of appreciation and wanting to help you improve and make more awesome stuff like this.
First: As strange as this may sound, I think your voice is too loud in this track, and it's a bit too dry as well. I think you could have re-balanced the vocals to be quieter dry and have a thicker, and maybe even darker since your voice is very bright on its own, reverb to suit how the piano and whistle are mixed.
Second: In the first half (weirdly only in the first half, not the second) your vocal harmonies and extra bits get lost in the main vocal. If you were to revisit the mix of this song, I would recommend giving just a slight volume boost to your harmonies and extra bits in the section starting around 1:00. Also the extra "wanted to fall" at 2:58 could do with a healthy boost - moreso than the first vocal section.
Third: The piano could use more presence in the lower end and a bit more of the foley from the piano wouldn't hurt either :) Hammer sound, string sounds, and seat creaks go a long way in terms of selling an authentic recording. Bringing the low end of the piano through would also help balance the brightness of your voice.
Fourth: This is a personal one so don't let it derail your creative vision. The switchup at around 5:00 - first of all don't get me wrong this section is hands down my favorite part of the song - I don't think there's enough payoff (payoff being the fast pace, lots of harmonies, forte piano, etc...). There's really only like 8ish bars of payoff and then we instantly revert back to the pace of the rest of the song. I think you could have extended it to 16 bars before reverting and building up to the switch back to the slow pace after building to the 16 bars of fast pace.
Lastly: There are just a couple places where I think you're a bit flat or don't have enough definition on each note in a run. If you have a plugin like newtone or melodyne load up your vocal recording in one of those programs and see the difference between what you wanted to sing and what you did sing. I'm not a singer and I haven't trained my ear for vocal pitch but there are a few spots where it does sound a bit off to me.
Here is what I noticed:
0:34 - "The" in "through the trees" is a tad flat
1:06 - at the end of "follow" I think you may have hit a totally wrong note, and the run itself lacks definition
1:15 - "of" in "forest of old" the harmony sounds sharp
That's about it for my criticisms. I just want to reiterate that I really enjoyed this despite all that stuff, but I honestly believe that this could have been taken up to an even higher level than it already is with a few small changes. Excellent work, huge love, biggups. I'm gonna watch out for more stuff from you!