This is a simply-constructed instrument with a fairly complex sound and functionality.  The piece of wood is screwed to the bowl so that it can move freely on a swivel and slightly up and down.  It is only touching the bowl on the attached side.  So, the other end dangles in the air above the bowl's edge.  The bowl sits on the player's lap and the string, attached through a tuning peg and a hole in the bowl. One hand plucks near the bowl's bottom.  With every movement, be it the left hand pressing down the string or changing the pitch by swiveling, the string gets tighter and looser, creating a beautifully unstable sound that does not differ much based on the way the string is plucked (except in volume).  

This instrument is also inspired by a sound from my childhood that stuck with me.  When I was in single digits, I was very fascinated with trunk buzz, the sound that's made when you have speakers in your trunk and the shit is so loud that the metal shakes and rubs against each other, creating this guttural metallic grunt in rhythm with the low frequencies in the music that's playing.  Of course, you just think the older kids are cool for having a car and being flashy.  But it was much more than that.  I don't quite like that sound in that context anymore.  But, I do still love the sound.  

If the wood board is swiveled all the way to it's loosest point, more and more grinding and rubbing takes place as the string vibrates much wider.  It touches the hook that keeps it in line with the board.  It touches the board itself.  The board touches the bowl and vibrates and the bowl acts as an amplifier for all of this.  The combination of the low pitch created by the loose string and the rubbing creates a sound akin that of the trunk buzz. Awesome.