A polyphonic harmonica with two rows of holes making the same sound. The height is the same. The two rows of holes on the accent harmonica are eight degrees apart, and the bottom one is eight degrees lower than the top one. Echo harmonica A tin sleeve is added to the back of the harmonica so that the sound produced when blown bounces back, creating an echo effect, but without the effect of a hand rattle. Contact number: 13867900203