I have fond memories from childhood of making a whistle out of a branch from a tree. When summer comes I’ll make one and post it here but in the meantime here’s a whistle I made from a scrap of wood using a CNC machine.

I made a quick design and cut it out. I held the pieces together and tried it. It didn’t work so I kept trimming it with a blade and chisel till it worked. I took note of the changes I made, then revised my CNC design. I cut another one out, glue it together and it worked! So I sanded it.