HAPI is basically a steel tongue drum. It falls into the class of instruments called idiophones. HAPI is an acronym for Hand Activated Percussion Instrument. When any of the steel tongues are struck, they vibrate at a particular pitch and create a sound. Various harmonics and overtones are generated due to the placement of the notes, which favours sympathetic vibrations. It can be played either with the hand or mallets. It is a highly resonating instrument, rich in middle frequencies and it fills surrounding atmosphere with a wholesome sound.
The sound produced is of a satvic quality, leaning towards rajas. The metal which generates the tone produces the slight coarsness of sound associated with the rajas quality.