Ektara

Ektara (literally "one-string", also called iktar, ', yaktaro gopichand) is a one-string instrument. It is most often used in traditional music from Bangladesh, India , Egypt, and Pakistan.
The ektara was a regular string instrument of wandering bards and minstrels from India. It is plucked with one finger. The ektara usually has a stretched single string. An animal skin is over a head made of dried pumpkin/gourd, wood or coconut. The neck is a pole or split bamboo cane. 
Pressing the two halves of the neck together loosens the string. This lowers its pants. The sound can be changed many ways by slight changes in pressure. 
The various sizes of ektara are soprano, tenor, and bass. The bass ektara, sometimes called a "dotara" often has two strings.