I am not a musician, although there are plenty of those in my family. I did play the violin for a year or so as a kid, but my piano skills were for years limited to one-finger versions of Incy Wincy Spider and one or two more other tunes.
However, a few days ago one of Dougie’s golf friends donated his old Yamaha PSR-530 keyboard to us, which made me study a couple of the GarageBand piano lessons that you get for free with a Mac.
After that experience, I felt a bit like I did when I was learning to drive – I kept asking myself why it was designed so badly.
However, a quick Google search taught me about the Jankó keyboard. You can read the details by following the link, but basically you can transpose a tune simply by shifting your hands.
It never seem to have become very popular, but there is a Japanese company making a similar MIDI keyboard. Here is a demonstration: