How do you play the vichitra veena?

On the vichitra veena, the left hand moves a glass ball called the batta along the main strings to set the pitch. The right hand wears two mizrab plectra, like those used for sitar, on the index and middle fingers, and the little finger plays the open chikari drone strings. Players put oil or butter on the strings to reduce friction under the slide; sources differ on which.