The idea here was to record something in one day that sounded like a band complete with vocals. Three things I learned while doing this:
Not bad at all! 
You might want to take a lesson from the bluegrass pros, though.
You do the picking and singing and hire a studio engineer to do the rest. 
Your ‘not so strong suit’ key of Bb is better than my best attempt in Bb! Great job! I’ve been trying (key word is trying!) to work in B and Bb lately… I know exactly what you mean!!
Is all done by you alone?? Oh wow, very nice!
Keep it going! This is great, and one of the best things you can do to make yourself better!
I’ll second what Ben wrote.
It’s a great way to push yourself!
Great job! Keep singing, you’ll get there. How many tracks was that in total, and what were they? You’re on the road to being a phenomenal harmonizer.
Great ear!
3 vocal tracks— lead, tenor, and baritone, and 3 instrument tracks— banjo, guitar, and mandolin. The lead and tenor tracks were both one take; the baritone took a few tries.
Nice! Looking forward to your next project.
Nice work! I enjoyed the listen and am impressed that you did the whole thing.
Wow, that’s impressive…and quite a challenge! Thanks for sharing this, and what an wonderful experience this must have been to see come together. 
That was awesome! Really enjoyed it!
I agree with Simone, your mandolin Bb is way better than I can do!
Nice work @Michael_Mark! Playing under recording isn’t easy! If I had to give a suggestion, I would say add some bass - not sure if you play bass, but I think it’d add a lot. But either way, good work!
Thanks, everyone! I did think about adding a bass track, but since I don’t own a bass, I’d have to use the GarageBand virtual one, which sort of seems like a pain. I might try it next time and see, though.
Where is Henry? He can help with that on the bass thing!
I can always cut a bass track for you also, if you ever need one.
Great job!! I have yet to sing in any recording projects.
It all sounded great, I would lose the vibrato in the vocals though. Sounds too refined for bluegrass, and too reverb-y (unless it was just reverb)