How Music Works

1. How Music Works: Acoustics for Musicians

Music Theory is not random or arbitrary. It’s based on laws of science and reflects the very structure of nature. As a musician, it’s important you understand the basics of how music actually works, as this will help you better appreciate why music theory is the way it is. By the end of this series of videos, you should have a basic grasp of how music works and why some things sounds good while other things sound bad.

2. What is Sound?

Sound is a wave, that is, it’s a vibration that travels through a medium, like air and water. Sound waves cause changes in air pressure as particles bunch together and spread apart. Now, we can’t see these ripples but our ears can hear them.

3. What is the difference between a Noise and a Note?

Both noise and notes are mixtures of sound waves at different frequencies. A note is made up of a ripple pattern which repeats itself over and over again in an ‘ordered’ way. While a noise is made up of individual ripples which have no relationship to each other and do not repeat - and so are ‘disordered’.

4. Frequency, Wave Shape and Pitch

Sound waves generally have four main qualities: Frequency, Wave shape, Amplitude, and Phase. Frequency (and wavelength, which is related) determine a notes pitch. While the wave shape of a note determines its timbre.

5. Amplitude, Phase and Envelope

Sound waves generally have four main qualities: Frequency, Wave shape, Amplitude, and Phase. Amplitude influences the volume of a sound (though it is a bit more complex than this), and determines its envelope. While the phase of two sound waves determines how they will interact, either reinforcing or cancelling each other.

6. Beats and Just Noticeable Difference

If we play two notes that are close to each other, we don’t hear two distinct pitches. Instead we hear a single note at the average frequency, but with a volume (amplitude) which goes up and down over time. This variance in volume is called a ‘beat’.

7. Why is A 440 Hz?

In the past, there was no international ‘standard tuning’. Over the past 500 years, the pitch of the note A (and therefore all the notes) has risen by about a minor third, but with large variations throughout. It was only at an International Conference in London in 1939 that the A above middle C was to be tuned to 440 Hz in all countries. This is known as ‘concert pitch’.

8. Do Drums Make a Noise or a Note?

Drums are circular, short cylinders with tight skins that have a tendency to produce notes – so they vibrate in a repeating pattern. And indeed, some drums, like an orchestral tympani are tuned to a particular note. A bass drum has skins at both ends and it produces a noise rather than a note. And the way you prevent it from producing a note is by tuning the skins to different notes.

9. The Overtone Series and Timbre

When you pluck the string, it doesn’t just vibrate back and forth at that one frequency. Actually, it vibrates at many different frequencies all at the same time. These frequencies are called 'harmonics' or 'overtones' and they determine the timbre of an instrument.

10. The Overtone Series and Dissonance

The Overtone Series determines whether two notes sound consonant or dissonant when played together. Further, the Major triad and the V-I Perfect Cadence are also both derived from the Overtone Series.

11. The Missing Fundamental

If a note is missing a harmonic, it doesn’t affect the pitch of the note - but only affects the timbre. Interestingly, even omitting the fundamental frequency only changes the timbre and not the pitch of the note.

12. Why are low notes muddy and high notes weak?

When you play a low note, most of what we can hear is actually the overtones of that note, and this is why low notes sound muddy. Whereas, we hear very few overtones on high notes as they are above our hearing range, and this is why high notes sound weak.

13. Inharmonicity and Octave Stretching

In theory, all overtones are just whole number multiples of the fundamental frequency. However, in reality, there may be overtones which are not whole number multiples of the fundamental. This is called inharmonicity. Inharmonicity occurs because strings are not perfectly flexible and contributes to the richness of the sound of a piano.

14. Infrasound & Ghosts

Some instruments can play notes that are below the normal human hearing range – which is called infrasound. But if we don’t hear these sounds, why do we use it? Well, interestingly, even though we can’t hear the note, we can still perceive it. And even more interestingly, infrasound may even explain ghosts.

15. Avoiding the 7th Harmonic

The 7th harmonic is a minor 7th that’s a little bit too flat. If the 7th harmonic is present, and it’s played with other notes from the diatonic scale it’ll sound really dissonant and out-of-tune. And for this reason we tend to try to avoid the 7th harmonic. That’s why you’ll find that the hammers in a piano are generally located near a node of the 7th harmonic.