Hohner 2504C Comet Octave Tuned Harmonica in Key of COctave tuned harmonicas employ the same horizontal division of the channel openings as tremolo tuned instruments and are also mainly used in folk music. They all feature the curved banana form and use the Wiener Octave Tuning, where upper and lower notes are tuned exactly one octave apart, resulting in a full, powerful sound without any tremolo beats. Our Octave harmonicas are all hand made in Germany. Tremolo and octave harmonicas are 2 voice