Prototyping a percussion instrument

I had an idea a while ago. I remember seeing an instructional video in which Bill Bruford was playing a complex rolling pattern between his toms and a tongue drum placed on his snare. For clarity, a tongue drum (sometimes called a slit drum) usually looks something like this. You've seen them.

I thought it would be cool to make a circular tongue drum. I played with a number of configurations of rectangular tongues, but finally realized that the shape was calling for a radial arrangement of wedge-shaped tongues instead. Like this.

I have a lot of baltic birch plywood around from cabinet projects, and so I took a first pass at a prototype using one of those panels.

To cut the interior kerfs and allow the tongues to vibrate, I drilled through at the endpoints of the lines and threaded a scrollsaw blade through the hole.

Once the tongues were cut, I cut outside the diameter mark on the bandsaw to complete the rough top. My scrollsaw technique is very rusty, and those inside cuts aren't up to production quality. Better to make the mistakes on the prototype.

I thought I would try pulling a strip of the plywood around the radius by kerfing its backside every half inch.

To cut the regular kerf spacing quickly, I hacked a quick jig onto the tablesaw mitre gauge.

That's a fat roofing nail, nearly a full kerf thick, with its head cut off. Each cut kerf fits over the nail to position the next pass. Very quick, very accurate.

I used the waste from the top as a clamping form to glue the side closed in a rough circle. I had counted on the material curving evenly, but of course it did no such thing.

To try to bring it into round, I cut some spacers and arranged them inside. It helped, but not enough.

I glued the top to the side while it was still clamped to the form.