Many of my videos are terrible. Many are experiments. Many are too short. Many are too long. I've deleted countless failures and I've re-issued some with improvements. Not everything has to be gold. This is the incredibly valuable lesson of music. A little effort every day and you can move mountains.
Transposition is a musical term for moving notes higher or lower to change key. So why do arrangers transpose? Why not keep everything in it's original key and for that matter why don't composers always write in C, as it has no flats or sharps? Choosing the key of a piece is somewhat like choosing a seat in an airplane. Though all the seats are sort of the same, everyone has preferences, for various reasons.
Piano rolls were paper tubes that made a player piano play a song. You would thread in one end of the paper roll -- kind of like an old film projector. As the paper fed through, little holes would tell the piano what notes to play. Fast forward a few centuries and meet digital music's digital equivalent: MIDI files.
Why do some people find playing a song very easy and others find it exceedingly difficult? I think it's because as we practice we are basically trying to crack the code of a piece. Some will understand it immediately, for some it takes a moment, and some never seem to get it. The best part of all, is once you have cracked one type, the next song in that style or genre is that much easier as you have the code partially cracked already. For that reason it's important to try many different styles of music.