What is Perfect Pitch?

You are probably already aware that perfect pitch, also known as absolute pitch, is the ability to identify or recreate a musical note without using a reference. Some musicians are particularly good at singing any pitch at will, others are great at transcribing anything they hear or tuning an instrument to concert pitch using perfect pitch. Many musicians are adept in both areas.

The Bryce Alexander Theory of Perfect Pitch

The important question is not that of “what?” but the question of “how?”. We all know what perfect pitch is, but how do this minority of people recognize these supposed elusive “qualities” of the notes? How does perfect pitch actually work and what are these qualities? Some of the world's most accomplished musicians do not have perfect pitch, however, most of us exhibit amazing skills of aural recognition every day. For example, we can easily recognize our mother's voice amongst hundreds of other voices and sounds, so why can't we hear the tone qualities between different notes?

To answer these questions, we need to understand a few basic acoustic principles. Firstly, every tonal sound from an instrument, voice, or any other source contains a fundamental frequency and several harmonics. Harmonics are sometimes referred to as overtones and are always present. Even if a single sine wave tone is generated and output to a speaker, there will be harmonics in the sound. This is because of the physical nature of waves to create other waves. The harmonics of a tone are multiples of the fundamental frequency. When you play an A440 on your instrument, the sound you hear is made up from 440 Hz, 880 Hz, 1320 Hz, 1760 Hz, 2200 Hz, and so on. Usually the fundamental (440 Hz) has the most energy, the second harmonic (880 Hz) has less, and the general trend is a decrease in volume as you count up the harmonics, although some instruments do take exception to this. Incidentally, the second harmonic is the same as the “first overtone”. This can get confusing so I am keeping with the terminology of harmonics.

Different instruments have different harmonic spectra. The following diagram shows the spectrum for a clarinet.

The general trend is a decrease in loudness from increasing harmonics but, also, the odd harmonics are louder than the even ones. Below, is the spectrum for a guitar.

As you can see, it is different to that of the clarinet.

Obviously, the harmonic spectra are different. The instruments do not sound alike at all. It is the levels of the harmonics of tonal sound, which (along with components of noise) give the particular timbre to the sound. We can easily tell the difference between a flute and a saxophone because they have very different harmonic spectra.

In summary, the unique “quality” or timbre of a tonal sound is always determined by its harmonic levels.

Getting back to the subject of perfect pitch, we know that musicians who have perfect pitch hear differences in “quality”, we might even say timbre, between the notes. We know a composer might choose the key of E flat for a sorrowful piece and F sharp for something more jubilant. So how does this fit in with the harmonic spectra of the notes when we know this to be determined by the instrument?

Click to go to the next page of What is Perfect Pitch?