What are split keys?

Have you seen an organ or any other kind of keyboard instrument which has more than 12 keys per octave? Here's a good picture of this kind of keyboard from up close. I remember when I first saw this organ in 2000, I was completely lost - I couldn't figure out the system behind the split keys. It took me years of research, education, and the right kind of practice to be comfortable with split keys.

In order to make your life easier, if you ever happen to play a similar keyboard, in this video I'm talking about what does this kind of keyboard mean, how the keys are arranged, how do you play it etc.