Musical instruments that start with the letter I include the igil, ipu, Irish uillean, Irish bouzouki, ichigenkin, inci, iya, itotele and istarski mih. The instruments originate from countries ranging from Cuba and Ireland to Croatia, Japan and the Philippines.
Bessel's functions are often used in acoustics for describing circular membranes behaviour (exploited by most of the musical instruments). They are the solutions of the wave equations using polar coordinates. Set the properties of the membrane Bessel's functions describe the vibrational modes of the membrane.
A serrated mussel shell edge can be used on wood much like a metal rasp. Shells were used to de-bark trees, and to chip out soft charcoal during some stages of canoe making. Mussel shells were used to make the blades of digging tools for agricultural work. A hole would be bashed through the middle of the shell and used to attach the shell to a wooden handle. The shell would be used much like a modern hoe blade (Fig 3). Shells were also used as scraping tools for shaping pottery.