Drumheads are attached by laces, which may be squeezed during a performance to alter the pitch.
The category also includes pellet drums such as the damaru, although not all pellet drums are hourglass shaped (such as the Korean do, nodo, noedo, and yeongdo, which are barrel shaped).
Hourglass drums exists in most regions of the world, but have very different construction methods, dimensions, purposes and playing methods.
Thus the designation of Hourglass drum is used as a category in general instrument construction and does not refer to any particular uniform instrument.
This article relating to membranophones is a stub.