A# is enharmonic (equivalent) to B-flat major.
(A# isn't used much because of all of the accidentals and double-sharps)
A# is an artifact from using the midi tables.

And if you look at this in Bb terms, it comes out to:
Bb G D, which is a raised 3rd (of 4th, or suspended)
which isn't a major triad

The major triad would be: Bb F D

I found this diagram more useful than the MIDI article mentioned.
https://djip.co/blog/logic-studio-9-midi-note-numbers
It was more compact.

I haven't checked all of the test cases, but it seems like there should be an augmented triad, and a diminished triad, to round out the possibilities. Also a suspended chord (R 4 5).
Also things like R 2 5, etc. Haven't analyzed what's there.

I think you should limit the kata to triads (including octaves of included notes), but not bigger chords. How would dominant 7 chord be classified, with major triad, but minor 7th, vs Major 7th.

Also, it would be good to summarize this part of music theory, rather than just pointing to a wikipedia page. I had a really good guitar teacher in highschool that explained this to me, but most people won't have that background.

2 [[8, -1], [6, -4], [5, 9]]
[8, -1, 6, -4, 5, 9] should equal [8, -1, 0, 0, 6, -4, 0, 0, 5, 9]
Is this Kata broken?
Or can someone explain the shifting such that:

Shift value: 2
Input: [[8, -1], [6, -4], [5, 9]]
Seems like output should be:
[8, -1, 6, -4, 5, 9] (3 arrays, of 2 elements each, with 2 shifts of 2)
8, -1,
6, -4
5, 9
which yields 6 elements

But, answer is:
[8, -1, 0, 0, 6, -4, 0, 0, 5, 9]
which is 10 elements, so the author must have a different definition of shift