One of my biggest worries was that I would need to find all the individual piano keys to make my notes, good thing the university of Iowa has all the notes from C0 to C8 (https://theremin.music.uiowa.edu/MISpiano.html). The difficulty now will just be in modifying the notes for them to last different lengths.
I also found a metronome implementation: https://gist.github.com/bzgeb/c298c6189c73b2cf777c.
And after those two minutes of searching this github page showed me another way Unity tracks time using AudioSettings.dspTime which is interesting.
With these two things already done for me I think completing the project will be much easier.