Here's a scenario. Let's say I use the public domain midi files to make professionally produced sheet music/tablature for teaching purposes.
I know I can sell these because I can do whatever with public domain. Also with various creative commons, I can do the same with a proper attribution.(except the "no commercial/no dreivatives version", right?)
Now there seems to be 2 types of copyrighted midis.
Copyrighted midis of copyrighted music.
Copyrighted midis of public domain music.
And this is where it gets confusing for me.
Well, the case 1. I think it's clear, that I can't produce sheet music/tab and sell these without proper license, which can be difficult to obtain. So here's the question 1.
Question 1. Can I, as a private music transcriber, take on a client who wants me to transcribe a copyrighted music using a midi file for their personal use at home, for the purpose of education?
Question 2. Can I do the same thing with the copyrighted midis of public domain music, as in serve as a private music transcriber for a client?
Added bonus discussion.
Many of the works I'm interested in are classical music composed centuries ago, yet there are midi files that are copyrighted. What is the reason for this? Is it because it takes work to produce the said midis? What's stopping me from making my own midi from old copies of the sheet musics and copyrighting the midis I produce?
Let's say I were to do take, then can I produce the sheet music and sell them online? And then use the midis for making electronic recordings or music videos or other derivative works to upload to video hosting sites like youtube and others?
Any help is appreciated