The mouth bow is an ancient musical instrument, surely one of the earliest, and is found in various cultures around the world. I was first introduced to the mouth bow when I lived for 6 months in Benin City, Nigeria, in 1981. My teacher there, Idemudia Izevbihen, who led a traditional music ensemble called the Ehengbuda Cultural Messengers, played the mouthbow, and encouraged me to play it. After leaving Nigeria, I didn't pursue playing the instrument any further, but I never forgot its appeal. Then, in the year 2008 I acquired a mouth bow and started playing again.
Many modern mouth bows are not actually bow-shaped anymore: the ones I play (one uses a metal string, and another a strip of rattan) are of this modern straight variety, and are both tunable, as well, another innovation of the modern musical bow.