In many ways, the harmonic series is the foundation of all music. It is through this naturally occurring series where we find the building blocks of timbre, pitch, and rhythm.

Also called the overtone series, the harmonic series is an ascending scale of pitches that emerge when a note is played on an instrument. For example, when the note C is played on an instrument, we not only hear that fundamental, but a whole collection of pitches asending above it. How these upper pitches, referred to as partials, harmonics, or overtones, interact with one another and how much energy each one has determines the color, or timbre, of the resulting sound. Put simply, the qualities and characteristics of the partials are how we know the instrument is a piano or an oboe or a violin.

As the harmonic series ascends, the overtones become closer and closer together. Because our culture uses equal temperament as our predominant tuning system, the harmonic series is not "in tune" with our this tuning system. Starting around the 7th partial, the frequencies are not in tune with traditional notation. Moving up in the harmonic series, overtones may be more than a 1/4 sharp or flat.