Oyster horn: The wind instruments, which have a cup-like opening, have a hole in the opening chamber which is responsible for the rapid passage of air into the inner chamber. Vibration of the lips creates different sounds from the body of the instrument. These types of instruments lack a tongue and sharp edge to produce sound. Also, have no holes for fingerprinting and sound changes, so they are called absolute wind instruments. But one or two sound holes on the body of some of these groups, can be seen. Among these group, we can mention Shahroud oyster trumpet, which is made of snail oyster and belongs to Garman village of Kharghan village of Shahroud functions of Semnan province. Appearance: The oyster horn is made of spindle-shaped oval shells that create a small chamber and hole for blowing at the top of the oyster. There is also a hole in the body for changing the sound Executive technique: Oyster horns have a simple technique, but in general, like trumpets, it is played. Of course, it takes a lot of pressure to play. The hole in the horn's body increases the volume of the shell horn by half to one curtain. Administration: In the past, it has been used as a news outlet as well as in military music. Oyster horns were played in the Nagharekhaneh, caravanserais, and baths. In the past centuries, it has been played in mourning groups along with drums and trumpets. Today, this oyster horn is used in mosques and only during Muharram mourning ceremonies.