Ivan Müller, sometimes spelled Iwan Mueller (1786 in Reval, Estonia – 1854 in Bückeburg), was a clarinetist, composer and inventor who at the beginning of the 19th century was responsible for a major step forward in the development of the clarinet, the air-tight pad. Müller's solution was the stuffed pad, originally made of kid leather stuffed with felt. These pads would "bulge", such that in combination with countersunk tone holes, would close the keyholes sufficiently tight to permit the use of an increased number of keys making the "clarinette omnitonique" possible.