Götz Rausch squats on a cushion on the floor of his workshop in Lunow-Stolzenhagen and lightly strokes the strings on a rectangular wooden box on legs. It creates a soothing, vibrating hum. Rausch, an instrument maker, then uses his other hand to adjust something beneath the box, creating a lightly buzzing sound. “This is a kotamo, a mixture of three different instruments,” he says. Rausch doesn’t need any sheet music to create the soothing tones from his combination instrument. “That’s just the great thing about therapeutic musical instruments. You can play them without taking long lessons to…