Probably not much difference - learning the different keys is a easy to talk about task, but you will spend a lot more time repeatedly practicing all the other things. If you were to teach someone to a high level but only the key of C, and someone else to a similar high level but all keys, and the end only a few weeks longer would be spent for the person learning all keys - and that person gets a lot more versatility.
Isomorphic is more logical and so easier to explain, but you still should be teaching the circle of 5ths to students. Once someone understands the circle of 5ths the layout of the conventional keyboard makes logical sense as well (it won't be as intuitive but the logic makes sense).
The only thing such keyboards are good for is transposing, and this one doesn't even help for all transpositions, only half of them. So you can learn something in one key, and then pretty easily play it in one of 5 other keys (note that transposing from e.g. C to D is trivial, but C to G is not). But that's about it.
It might have some minor advantages, but there are probably also disadvantages: this doesn't help you learn the different modes (minor, dorian, etc.). Instead, they might be hindered by your muscle memory.
So, for comping it can shine, but for normal music, probably a disadvantage. I certainly don't see any advantage that should make everybody switch.
So do you think if people designed a keyboard from scratch, they would come up with the same traditional layout?
It seems to me that the standard piano layout (and the standard musical notation, which is basically piano tablature) is the result of cruft being added over time rather than refactoring to better express the underlying concepts.
.. these notes seem to work well for our gloomy church chants, let's call them A, B, C, D, E, F, G
.. hmm, maybe focusing on a more cheerful mode is better, so obviously we'll tell everyone to start from C rather than A
.. it seems that some of our intervals are roughly double the other intervals, let's add in the extra notes as C#, D#, F#, G#, A#, we won't bother telling the kids what happened to E# and B# though 'cause that's too hard to explain
.. 12tet incoming, we'll just retune our existing instruments slightly
Instruments and music theory are largely based around 12TET nowadays, but it seems like it's tacked on top of something else.
> So do you think if people designed a keyboard from scratch, they would come up with the same traditional layout?
That depends on the constraints. Today's keyboard is a good compromise even today. You can compromise different things, but a full micro-tonal keyboard isn't enough better as to be worth it for most things and once you agree that you must compromise the only question is what. A 9:8 or 10:9 major second are both of rare use and so you probably just agree to get rid of them. The only hard part is 3rds, would you accept how bad they sound in a the current system (in which case a true 5th and a equal tempered 5th are close enough), or try to divide the thirds somehow.
I don’t know of any comparisons, but anecdotally, I play both piano and button accordion and my guess is that piano keys would be easier for beginners, due to the direct mapping to sheet music. Beginners start in C major using just the white keys and then added sharps or flats are the black keys. (Then you learn to play in other keys, but gradually.)
A chromatic button accordion has other compensating advantages but I don’t find either one easier overall. They’re just different. You get better with practice.
Piano teachers today sometimes start in other keys that are easier to play scales in than C Major like B major and D-flat major! And this way kids aren't "scared" of the black keys--they start with them.
On guitar in fourths tuning, you only need to learn each interval and chord shape once, compared to multiple permutations in standard tuning. Not sure how much difference this makes over the long run as another poster pointed out, but for me it made the process seem much less overwhelming and motivated me to start learning how to make my own chord voicings, which is something I wouldn't have done in standard tuning.
> Not sure how much difference this makes over the long run
I tune in all fourths as well. For me it has made a huge difference since I made the jump some years ago. Putting voicings, patterns, etc., into muscular memory is faster and a lot less work. For my purposes, it makes the instrument more intuitive with a better ear-hand connection. Even very advanced players trip on the G-B strings oddity (with things like playing a fast, angular melody on different string sets, without preparation, for example).
It's really nice to play a scale, come to the octave, slide, and keep on playing the same shape across the higher strings. It's made the fretboard feel a lot more transparent to me.
