Another very distinctive sound of Gagaku is the harmonica-like sho, which provides a kind of cloud of sound. The shape of the instrument is supposed to suggest the mythical bird, the phoenix. The sound is said to express the feeling of light shining from the heavens. The sho is used in instrumental music and dances of the left and usually plays chords to provide harmony, a technique called "aitake (combined bamboo)." However, in Saibara and Roei a technique called "ichichiku (single bamboo)" is used to play melodies.

The instrument is 50 cm. long and 7 cm. in diameter. The body of the instrument is called the kashira and is made of a bowl of Japanese cypress or cherry with a cover of water buffalo horn. Around the edge of the body are seventeen pieces of bamboo of various lengths about 3 - 4 cm. in diameter. Each piece of bamboo has a copper reed attached to the bottom end, in the part hidden by the body of the instrument. When the instrument is blown, the air makes the reed vibrate in a manner similar to the harmonica. But even though there are seventeen pieces of bamboo, reeds are only attached to fifteen and two make no sound whatsoever. It is thought that originally all of the pieces of bamboo had reeds, but because these two were not used, gradually reeds disappeared from these two pieces of bamboo. There are holes on the pieces of bamboo and a very complicated method of fingering so that different chords are produced as the player inhales and exhales to make a continuous sound. Before the instrument is played, it is heated over a charcoal fire. This eliminates any moisture that may have accumulated inside the instrument and prevents the pitches of the pipes from being altered or the reeds not sounding.