[8bitsrule]

IANAL either, but. For MIDI, a public-domain work might be just mechanically converted into notes of a 'MIDI score'. Probably very flat-sounding, but technically that transcription [0] may (probably) be PD.

(E.g. My handwritten copy of a PD short story is probably PD. But my reading of it isn't.)

BUT if some famous piano player performed for the MIDI recording, then you've got tempo changes, timing, attack velocities, all that data in the file as well. Probably not PD (best to ask). (As with piano-player rolls.)

[0] https://en.wikipedia.org/wiki/Transcription_(music)

[999900000999]

Sounds like someone needs to be awesome and release midi files of classic compositions.

You have the rare hip hop song which samples classical music directly, but I really want to learn music theory, like understanding how the notes work.

[8bitsrule]

The classics are out there, but often they've been performed by someone. Easy to strip down to the notes with a good MIDI editor.

It's been a long while for me, but a search on 'classic midi files' turned this up. (Hard to tell if it's crap without a listen.) https://www.midiworld.com/classic.htm