This double ocarina plays an octave in the minor pentatonic scale, with the second chamber acting as a drone, with 2 drone notes possible. Because of the separation of the two chambers, the acoustic effect on the player is enchanting.
Pentatonic vs. Chromatic
The minor pentatonic tuning is such a beautiful scale, and provides this tradeoff: with the double pentatonic, every combination is harmonious (you can produce an interval of a second, which is harmonious once you make friends with it). What you lose in comparison with a chromatic ocarina is that you do not have every note of the scale, so you are limited in what you can play. If you want to play specific songs, video game tunes, classical pieces, or most traditional folk songs from around the world, you will want a chromatic ocarina, which is capable of more complex tunes, but also requires more practice to sound beautiful. That being said, even if you are an expert player of chromatic ocarinas, you will still enjoy playing and exploring music with the pentatonic style ocarinas.