SMB theme played on a Melodica
Here's a dude playing the SMB theme on a Melodica wearing a Mario cushion as a hat.
"The melodica, also known as 'blow-organ' is a free-reed instrument similar to the accordion and harmonica. It has a musical keyboard on top, and is played by blowing air through a mouthpiece that fits into a hole in the side of the instrument. Pressing a key opens a hole, allowing air to flow through a reed. The keyboard is usually two or three octaves long."