The performance method is easy and makes the room for the mouthpiece of Ocarina with both hands.
The capacity of the both hands is changed and a pitch is determined.
Look at a demonstration animation of "O-Tone" put in YouTube.
"Le Cygne" : Saint-Saens http://www.fl-oca.com/eng/edata.htm
Ogawa Kenji will suggest from several years before,
and this method is used for a performance, recording, etc.
The person who heard my CD and was wanted to learn the performance method.
In order to reply to your request, it is named "O-Tone" (Ogawa Tone) and announces here.