Find anonther kata to turn into code golf, and avoid the issues highlighted below - I will be one of the first to try it! ;-)

Too long: False should equal True

Golf kata should really show the stats in the tests. We're not going to count the chars ourselves.

Suggestion part (but consider it like a very STRONG suggestion):

Most users are familiar neither with music nor with guitar. So, if I'd say that there is almost all what's needed about the music/notes part (let's rather say that most of what's missing is close to an acceptable notion of "general knowledge"), you have to at least explain what you mean by

There are diferent tunings, but they are all standard

...hence, the steps from low to high pitch is always 5,5,5,4,5 semi-tones between the strings, whatever the tunning is. Just give the info, there is absolutely no point hidding that one search away. You'll just irk the users and get more down votes on your kata.

Issue part:

You have to say that all notes of a mode will be present and that there are no ambiguities about what mode is used. That's part of the sepcifications: without that, the description is incomplete.

Cheers