It was not until I joined a choir in my teens that I realized people with absolute “perfect” pitch exist... oh how naïve I was!
The ability to distinguish a note without reference intrigued me – how do they know and what defines a music pitch anyway? Why do different instruments sound different? Here’s a brief introduction to the science and origin of music pitch so you don’t have to stay clueless like I did.
Physics of sound frequency
Sound refers to the longitudinal waves produced by a vibrating object that travels through a medium (i.e. air, water, glass) and eventually reaches a listener. It is globally measured in Hertz (Hz), the number of wave oscillations (vibration) per second, or simply sound frequency. Pitch then refers to a particular position in a frequency range – a low pitch has a relatively low frequency and vice versa. A healthy individual can hear between 20 Hz to 20 kHz, well encompassing the frequency range produced by a full orchestra. Every object also has its own natural frequency, the rate at which it automatically vibrates when disturbed.
If you ever heard a random object buzz while practicing your instrument or felt the floor vibrate during a chamber performance, it is perfectly normal! Such phenomenon is known as resonance, where your instrument sound matches the natural frequency of the surrounding objects thus “disturbing” them and causing a vibration. One day I was wondering why the F5 key on my piano sounded oddly metallic, only to find that it resonated with the aluminum light shade beside my piano. How bizarre.
Music is more than the fundamental
If a pitch is just a frequency, why does an A4 on the piano sound distinctly different from an A4 on the viola? That is because a music pitch is usually made up of a spectrum of sound frequencies in addition to the fundamental frequency, giving each a unique sonority.
Overtone and harmonics
The pitch A4 has a fundamental frequency of 440 Hz and every time you play it, frequencies of its multiple (A5 = 880 Hz, A6 = 1760 Hz etc.) ring simultaneously. These are called overtones or harmonics and collectively they produce the single note you hear. The fundamental frequency will always be the loudest, so each pitch remains discernable. Overtones occur naturally and are commonly observed in string instruments where they vibrate in a series of modes. You can also hear overtones in chamber music especially when each instrument is producing a clean and pure pitch that creates the right amount of upper frequency overlap required for overtones.
As a former chorister, I get excited whenever I hear a faint note of an octave higher than our singing register – producing overtones is an indicator of achieving “perfect harmony” in music. Once, my conductor mistook someone for singing an extra note, when it was just an overtone!
Not all harmonics are equal either – the quality of each overtone AKA “timbre” varies between instruments. Musicians also refer to timbre as “color” or “tone”, which is shaped by a multitude of factors: material, shape, and build of an instrument, hall acoustics, playing techniques, humidity and so on. As sound reflects and transmits through the surrounding objects, the cumulative harmonics become altered, causing us to perceive some music as “rich”, “thin”, or “noisy”. Musicians often utilize timbre to express a particular mood or musical idea – a pianist depressing the una corda pedal creates a muted sonority and varying the bow speed and contact point on a string instrument can change the tone.
Origin of standard pitch
Did you know that A4 has not always been 440 Hz? Instrument tuning centuries ago had no pitch standardization so you might find a 1511 German modern organ with A=377 Hz or a Middle Ages pipe organ with A=567 Hz (see further readings). In fact, some composers had specific pitch preferences – Handel liked A=423 Hz and Mozart at A=422 Hz. As radio music broadcasting popularized in the early 20th century, musicians began noticing the nuances of classical piece recordings and collectively sought for a standardized concert pitch. A=440 Hz as we know today was eventually set in 1939 as a result of the pursuit for global music coherency.
Admittedly, the notion of pitch is highly complex but comprehending it could increase our appreciation and perceptiveness for classical music. I hope this brief article enlightened you and do check out the further readings for in-depth discussion about music pitch.
Be kind & keep striving!
Cavanagh, L. (2009). A brief history of the establishment of international standard pitch a=440 hertz. Webzine about Audio and Music. http://www.wam.hr/sadrzaj/us/Cavanagh_440Hz.pdf
Pell, A. (n.d.). What Are Overtones in Music? Musical Instrument Pro. https://musicalinstrumentpro.com/what-are-overtones-in-music/
What is Sound? (n.d.). PASCO Scientific. https://www.pasco.com/products/guides/sound-waves