Yes, it sounds too good to be true, yet it is true.
I play diminished tuning exclusively. There is also augmented tuning which has four patterns.
You can start the tuning on any note.
C dim tuning would be:
hole 1: C, Db, D, Eb
hole 2: Eb, E, F, Gb, and so on...
Every draw button is the same note as the blow in the next hole to the right, giving you 4 evenly spaced enharmonics throughout the octave.
It's a symmetrical, or fixed interval tuning, which means each interval will be created with the same breath & button pattern regardless of where you are on the instrument.
There are still 12 keys of course, but the patterns repeat themselves every minor third, so playing in C is the same as playing in Eb, Gb, & A. You simply move one hole to the right and you are up a minor 3rd.
There are several reasons why the tuning is not more popular yet. They are not readily available except through Seydel's harp configurator. If you want a different model you have to special order, replace reeds, or retune them from solo tuning.
Also, once players become accustomed to solo tuning, they are less likely to want to 'start over' with a new tuning.
I am happy to answer any and all questions you may have, so fire away.
Grant
