Shruti Box

The shruti box is a very simple drone instrument. It is often used to escort Indian wind instruments particularly flute. One side of this instrument has the bellows. By pumping this with one of your hands, air flows into the reeds housed on the opposite side. Each hole where the brass reed is placed has a movable plug. By rotating these one can open and close the air flow. Hence, opening the flow will make the reed sing and closing it will mute the sound. The shruti box probably originated from the harmonium.