Noun
a small rectangular free-reed instrument having a row of free reeds set back in air holes and played by blowing into the desired hole
Source: WordNetmouth-organ
He also stated that the actual instrument in use was a one-octave mouth organ concealed under Home's large moustache and that other one-octave mouth organs were found in Home's belongings after his death. Source: Internet
Occasionally a more talented child may do card tricks, play the mouth organ, or something even more impressive, but most children will earn plenty of treats even with something very simple. Source: Internet