Every note that is played on an instrument is really a combination of several notes or “harmonics”, even though we may not realize that we are hearing more than one note at a time. Play the lowest C on the piano. Now find the next C which is an octave higher. Press this key very slowly so that it does not sound and hold it down. While holding it down play the bottom C again making it loud and very short. The C that is being held silently will now sound. This is because the strings of that C are vibrating a little because it is a harmonic of the low C (they can vibrate because the damper is off the string while the note is being held down). The same can be done holding the next G down, then the next C, then the E. The higher the note the fainter (quieter) the harmonics become. The musical example below shows the notes of a harmonic series in musical notation. 