Does combining the parts of the Song of the Hero the three dragons sing in their respective cutscenes, along with the final part sung by Levias, actually yield the Song of the Hero?
Bonus question 1: Does the Tadtone score match the rhythm of part 1 of the Song of the Hero?
Bonus question 2: Is the song heard during the "all Tadtones found" cutscene actually part of the Song of the Hero?
Bonus question 3: Are the vertical positions of the Tadtones on the score accurate to the Song of the Hero?
While searching for the Song of the Hero and the 4 parts that supposedly combine into it, I found a YouTube video that actually answers the question itself:
And the answer to the question is: Yes, the 4 parts, when played together, actually do form the Song of the Hero.
Unfortunately, my knowledge about musical scores isn't nearly good enough to answer any of the bonus questions, but comparing the score as it appears in-game:
to an actual music score I found online (you can hear the score being played here):
the in-game score appears to match the actual score closely enough.
The rhythmic notation, on the other hand, isn't as straightforward.
In the game, we have quarter notes, as well as 1/8 and 1/16 notes:
Images taken from studybass.com
The game renders 1/16 notes with only a single beam instead of using double beams. It also combines multiple groups of 1/16 notes into a single group featuring 8 and 16 notes respectively, though I don't know if that's a valid notation or not.
All in all, the in-game notation appears to be consistent and seems to match the tadtone melody.
Note that the final part of the in-game score doesn't quite match the one on the "real" score, but that's also because the rhythm and melody deviates a bit. For comparison, here's the "actual" tadtone melody, as it is played in the game:
