Unlike almost all other drums which have a convex (curved outward) or flat surface, the steelpan is hammered into a concave (bowl-like) shape. This 'sinking' of the drum is the first step in its creation. Each note is then hammered back up slightly from the bottom, creating localized 'domes' on the surface. When struck, these domes vibrate independently. This unique geometry allows a single piece of steel to contain dozens of different notes that don't interfere with one another.