Musicians, audio engineers and music producers are always discussing about pitch, whether they realise it or not. In fact, the study of pitch and how it relates to human hearing is so important, that scientists have been researching on it for decades. So, if you are an aspiring recording artist or audio engineer, then the very important question you need to be asking is – What is pitch in music?
In today’s article, we will touch on the fundamental concepts surrounding the subject of pitch, in relation to music and how the audience perceives them. You will also understand more on how pitches are labelled and how it relates to musical instruments. As with all my other articles, I intend this one to be very beginner friendly. So are you excited to know more about pitch!? (Yes, I know you are) Then, let’s start!
What is Pitch? – The Introduction
The perceptual property of sounds that allows them to be in a certain order, in relation to a frequency-related scale, is known as “Pitch”. To put it simply, “pitch” is what makes it possible for you to hear sounds as “higher” or “lower”, in a sense associated with musical melodies. Pitch can only be discerned in sounds with frequencies that are clear and stable enough, for it to not be noise.
Together with duration, loudness, and timbre, pitch is also a major auditory attribute of musical tones. Pitch may be described as a frequency, however it is also a psycho-acoustical attribute (subjective) of sound, and not just a purely objective physical property.
Throughout history, pitch and pitch perception has been intensively studied by scientists and it remains a central, major issue in psychoacoustics. The understanding of pitch has played a pivotal role in helping researchers to formulate and test various theories of sound representation, processing, and perception in the auditory system (by humans and also animals).
Now, let us look into the various concepts surrounding pitch that we will cover:
- Perception of pitch
- Definite and indefinite pitch
- Pitch standards and standard pitch
- Labelling pitches
Perception of Pitch
This particular topic that we are about to cover can get a bit lengthy. The concept of pitch perception can be a little bit confusing if you are new to it. Hence, to make it much simpler for my highly-valued readers (yes, I love you guys), this section will be further divided into four parts:
- Pitch and frequency
- Theories of pitch perception
- Just-noticeable difference (JND)
- Aural illusions
Essentially, pitch is an auditory sensation. It is the result of your brain assigning musical tones to positions relative to a musical scale, based fundamentally on its perception of the frequency of vibration. Pitch and frequency are not equivalent, but they are closely related. Frequency is a scientific component that can be measured objectively, unlike pitch, which is subjective and cannot be directly measured. Keep in mind that this doesn’t imply that the majority can’t agree on which notes are “higher” or “lower”.
Pitch is not-existent in sound waves themselves, but a frequency can be obtained by measuring its oscillations. Only the human mind is able to map out the internal quality of pitch. However, pitches are often quantified as frequencies in cycles per second (or hertz), by comparing to sounds with pure tones (waves that only consists of a single frequency), which have periodic, sinusoidal waveforms. Thus, more complex sound waves can then be assigned a pitch by this method.
The American National Standards Institute, defines pitch as the “auditory attribute of sound according to which sounds can be ordered on a scale from low to high”. Pitch, being very closely related to frequency, is entirely (almost) determined by how fast the sound waves are making the air vibrate. Other aspects of the sound wave such as intensity and amplitude, have little to no effect on pitch. Hence, “high pitch” means very fast oscillation, and “low pitch” corresponds to slower oscillation.
In some cases, pitch (to a very limited degree) is affected by the sound pressure level (loudness, volume) of the tone. This normally occurs at frequencies below 1,000Hz and above 2,000Hz. Pitches of lower tones will get lower when sound pressure increases. Let’s take for example, a very loud tone of 200Hz (high sound pressure) will be perceived as a semitone lower in pitch than if it is just barely audible. Anything above 2,000 Hz, the pitch will get higher as the sound gets louder.
Theories of pitch perception
Scientists formulate these theories in order to explain how the physical aspect of sound and the physiological make up of the human auditory system work together to produce the perception of pitch. By and large, pitch perception theories can be further divided into “place theory” and “temporal theory”.
“Place theory” holds that the perception of pitch is determined by the place of maximum excitation on the basilar membrane. In order for high frequencies to be perceived, place theory (taking into account the tonotopy of the auditory system) must take effect, since neurons have an upper limit on how fast they can phase-lock their action potentials. However, the flaw in place theory is that, it cannot determine the accuracy of pitch perception within the low and middle frequency range.
“Temporal theory” offers an alternative that relates to an action potential’s temporal structure. It mostly focuses on the “phase-locking” and “mode-locking” of action potentials to frequencies in a stimulus. It is still debated as to how exactly, the temporal structure helps identify pitch at higher levels, but the autocorrelation of action potentials in the auditory nerve, seems to form the basis of the process. However, a neural mechanism that can accomplish a delay (a necessary process in autocorrelation), has not been found.
Just-noticeable difference (JND)
Also known as “JND” for short, it represents the threshold at which a change can be perceived (which depends on the tone’s frequency content). Below 500Hz, the JND is about 3Hz for sine waves, and 1Hz for complex tones. Anything above 1000Hz, the JND for sine waves is about 0.6% (about 10 cents). JND is often identified by having two tones to be played in quick succession, with the listener trying to hear a difference in their pitches.
Also, the JND will be smaller if the two tones are played simultaneously. This is because, the listener will then be able to discern beat frequencies (interference pattern). The total number of pitch steps that is audible in the range of human hearing is about 1,400. The total number of notes in the equal-tempered scale, from 16 to 16,000Hz, is 120.
This refers to the misleading perception of pitch. There are several examples, such as the “tritone paradox”, which involves a pair of Shepard tones (a sound consisting of a superposition of sine waves separated by octaves) played sequentially and separated by an interval of a tritone, or half octave. This can be heard as ascending by some listeners and as descending by others.
Another very well-known example of an aural illusion is the “Shepard scale”, where “Shepard tones” are played with the base pitch of the tone moving upward or downward. This creates an effect where the sound appears to continue ascending or descending forever.
There are some musical instruments that do not produce notes with a clear pitch. For instance, an unpitched percussion instrument (like a snare drum or bongo drum) does not produce any particular pitches. A sound or note that can be considered to have a definite pitch, is when a listener can very easily identify the pitch. Take note that sounds with a definite pitch, have a harmonic frequency spectra or close to one.
Any sound generated on instruments will produce many modes of vibration (occurring simultaneously). You are actually hearing many frequencies at once. The lowest frequency in the sound is called “fundamental frequency” and the higher ones are “overtones”. Harmonics (an important class of overtones) are frequencies that are integer multiples of the fundamental.
Regardless of whether higher frequencies are integer multiples, they are collectively referred to as “partials”, indicating the different sections that forms the total spectrum. An indefinite pitch is defined as a sound or note that a listener finds almost impossible or very difficult to identify as a pitch. Sounds with indefinite pitch do not have a harmonic spectra (or have an altered harmonic spectra), which is known as “inharmonicity”.
Pitch standards and Standard pitch
A pitch standard is also known as “concert pitch”. It refers to the conventional reference of a pitch, that a group of musical instruments are tuned to, before any performance. Depending on the musical direction of the performance, concert pitch can vary from ensemble to ensemble, and has varied widely throughout history.
Standard pitch is a universally accepted convention. The musical note A, above middle C, is set at 440Hz (often seen as “A=440Hz” or in some cases “A440”). Frequencies, such as 442Hz, are also very commonly used as an alternative reference pitch. Another standard pitch, known as the “Baroque pitch”, has been standardized in the 20th century as A=415 Hz (precisely a semitone lower than A440, in order to facilitate transposition).
Transposing of instruments are in part, responsible for the creation of various pitch standards. In musical practices today, musicians often find themselves transposing their parts into different keys from voices and other instruments (and even from one another). Due to this, musicians need a standard pitch to refer to unambiguously, in order to effectively communicate with each other.
In the musical and scientific world, pitches have to be labelled in order to be easily identified and communicated, especially among musicians and researchers alike. There are three forms of labelling:
- Letters (Helmholtz pitch notation/western chromatic scale)
- Scientific pitch notation (combination of letters and numbers), where notes are labelled upwards from C0 (16Hz “C” note)
- Numbers representing the frequency (number of cycles per second) in hertz (Hz)
Lets take for example, the note A (above middle C). It is often referred to as “A4” or “440 Hz”. Take note that in standard Western equal temperament, identification of pitch is not affected by “spelling”. For instance, “G4 double sharp” refers to the same pitch as “A4”, but in other non-western or alternate temperaments, these two notes may be different pitches altogether.
Human perception of musical intervals (the difference between two notes) is approximately logarithmic with respect to fundamental frequency. For example, the perceived interval between the pitches “A220” and “A440” will be the same as the perceived interval between the pitches “A440” and “A880”. Because of this phenomenon, music theorists will use a numerical scale (logarithmic in relation to fundamental frequency) to represent pitches.
There are various tuning systems that determines the relative pitches of every note in a scale. The most common organization system, is the twelve-note chromatic scale (used in the west), with equal temperament now used as the universal method of tuning that scale. Within that scale, the ratio between any two successive notes (pitches) is precisely the twelfth root of two (about 1.05946).
In “well-tempered” systems (most notably used by Johann Sebastian Bach), various methods of musical tuning were utilized. The “octave”, is one interval that is commonly shared by almost all of these systems. An “octave” is where the pitch of one note is double the frequency of another. For example, the note A above middle C will be 440Hz, thus the A note that is an octave above that would be
That is all I have for you guys for now. I hope you had a rather enjoyable time reading this article, and have benefited from it as a result. I will definitely look into producing more articles that are relevant to this subject in the future, so stay tuned!
Do leave comments or questions below and share with your friends if you like!