Overblowing is an important modern technique among players of some harmonica types, notably the standard Richter-tuned harmonica or blues harp. Combined with note "bending", it yields the full chromatic scale across the instrument's range. Though pioneered on Richter-tuned harps, overblowing, or the related "overdrawing", is possible on any harmonica having both a blow reed and a draw reed mounted in the same airway (i.e., behind the same mouthpiece hole), but no "windsaver" valve on the higher-pitched of the two reeds. While superficially resembling in its pitch-jumping effect the overblowing of other (beating-reed, aerophone, brass) wind instruments, harmonica overblowing is completely unrelated from the standpoint of the underlying physics. It does not induce the sounding reed to sound a higher overtone – free reed overtones do not even begin to approximate the harmonic series nor are they particularly musical – nor does it induce a higher vibrational mode in air in a pipe or other resonator – harmonicas generally have no such resonator. Rather, it silences the sounding reed while eliciting sound from the formerly silent one – the one that normally responds to air flowing in the opposite direction. A key fact for understanding both overblowing and "bending" on such an instrument: a free reed mounted over a reedplate slot will normally respond to air flows that pull it initially into the slot, i.e., as a "closing reed", but, at only slightly higher air pressure from the opposite side, will also respond as an "opening reed"; the resulting pitch is generally just less than a semitone higher than the closing-reed pitch.