The concept is similar to a wooden tongue drum. When a tongue is quickly and lightly struck with the finger or mallet, it vibrates creating sound waves. Playing a HAPI is similar to playing the Hang Drum, though the similarities end there, as it is a totally different type of musical instrument. By changing the shape and length of the tongue, optimal vibration and perfect tone is achieved. By arranging the notes in a unique way each note, when struck, excites surrounding notes that are musically compatible with it. This adds to the harmonic spectrum of the tone. Rather than just one tone it can now create a spectrum of supporting sound for each note. The tone is similar to singing bowls or musical bells which create multiple harmonic overtones. The body of the drum acts as a resonating chamber adding depth to the note. An opening port in the bottom of the drum serves three functions. The bottom hole allows the sound to escape and increases the volume. It releases the tone from the body so that the notes do not overlap each other too much.