I was from the eastern part of the US, travelling westward with my wife and son. I was an musical instrument maker, mostly wooden flutes and guitars. I had a practice of using very substantial wood when carving the flutes and the necks of guitars and mandolins. When we reached the west coast, my son was studying with another instrument maker and showed me a technique he learned about carving out the flutes and the guitars and mandolin necks where he made the walls very thin. Next, he would create a very thin and long piece of wood like a very long tooth pick that he called the heart string and attached it inside of the neck or inside the flute. This created a vibrating counterpoint to the instrument that increased it’s harmonic potential.