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I feel that it would be a great learning tool.



The best learning tools are those that match your learning style. If it fits your learning style, then it's a good purchase. (ever go to a book store and read through a bunch of instructional books until you find one that speaks "your language?" Same thing. ) Likewise, in school you almost certainly learned better from teachers whose teaching style matched your learning style. We don't all learn the same way.

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I always thought it would be nice (and this might be available) to have a synth, say you're playing in C, the synth would then block any notes that were not in the C scale (or whatever key). A person that was, say a guitar player with a fair knowledge of music, knows a few keys on piano, could fake a lot of stuff like that.



That's pretty much the way some vocal processors work. The TC Helicon Voiceworks, for example, also has an instrument jack. Playing an instrument through it could yield the following results:

1) auto harmony to the played note
2) correct the played note to fit a specific scale/mode
3) correct the played note to a specific MIDI passage
4) correct the played note to some note in the current MIDI chord
5) harmonize the played note to something valid in the current MIDI chord

etc

Also, some DAWs have a midi offset on each track that you can use in real time. You can play in C then offset it to another key. Or you can record in C then transpose it to the other key.

https://www.dropbox.com/sh/ey71h8ep047758h/AAC12jNM0Hz9Q8zsh5iDeqNHa?dl=0