=> Harmonium is a musical instrument which is a free-reed organ that generates sound as air flows past a vibrating piece of thin metal in a frame. => Smooth Playing - You don't have to lift you fingers if you wanna play next or previous key, you just have to slide your finger smoothly on it. => Coupler - Coupler provides the effect of richness in the sound of the harmonium by adding sounds of an octave higher notes to the notes which you play. => Zoom In / Zoom Out Keys - Use the Plus / Minus