The instrument has the sound leaving the sound board passed through a chamber produced by a flexible outer wall which has a pattern of outlet holes (8). A separate resonance chamber (1) inside the main chamber is divided by a central wall (2) with variable edge spacing to the resonance chamber. Sound passing through the resonance chamber is delayed slightly and exits from holes (8a, 8b) to mix with sound which passes unimpeded from other holes (8c). The mixing of the sounds produces a richer tone by the reduction of overtones and higher frequencies through the mixing of the phase shifted sounds. The resonance chamber has a variable inlet slot (7) whose shutter (9) is controlled by a linkage operated by the elbow of the player. The outlet holes have sliders to adjust the relative apertures and to provide fine adjustment to the tone.
