Sound
Before Music, There Is Vibration
What Is Sound
Sound is vibration transmitted through a medium. When an object vibrates, it displaces the air molecules around it, creating alternating regions of compression and rarefaction that propagate outward as waves.
These waves reach your ear, cause your eardrum to vibrate in sympathy, and your brain interprets the signal as sound. Everything in music — every chord, every melody, every texture — begins here: a thing vibrating in air.
Frequency
physicsThe number of complete vibration cycles per second, measured in Hertz (Hz). Higher frequency = higher pitch. A4 = 440 Hz is the standard tuning reference.
Amplitude
physicsThe magnitude of displacement in a sound wave. Greater amplitude = louder sound. Measured in decibels (dB).
A guitar string vibrates at 330 Hz. What note is this closest to? If you double the frequency, what interval do you produce?
Pitch & Frequency
Pitch is the perceptual quality of a sound's frequency. It is how we experience high and low. A flute playing A4 and a violin playing A4 produce the same frequency — 440 Hz — but we hear different timbres.
The relationship between frequency and pitch is logarithmic. Doubling the frequency raises the pitch by one octave. This means the distance from 100 Hz to 200 Hz sounds the same as 200 Hz to 400 Hz. Our ears hear in ratios.
Octave
intervalThe interval between one pitch and the next pitch with double or half its frequency. The most consonant interval. Any two pitches an octave apart share the same letter name.
Timbre
physicsThe quality that distinguishes different sound sources playing the same pitch at the same volume. Determined by the harmonic overtone series unique to each instrument.
If A4 = 440 Hz, calculate the frequency of: a) A5 (one octave above) b) A3 (one octave below) c) E5 (a perfect fifth above A4)
The Harmonic Series
When a string vibrates, it doesn't only vibrate as a whole. It simultaneously vibrates in **halves, thirds, quarters, fifths** — every whole-number division. Each division produces a harmonic overtone above the fundamental pitch.
The harmonic series is nature's chord. The first six harmonics of any pitch produce a major triad. This is why the major chord sounds "natural" — it exists in the physics of a single vibrating object.
Fundamental
physicsThe lowest frequency produced by a vibrating object. The pitch we identify and name. All overtones are integer multiples of the fundamental frequency.
Harmonic Overtones
physicsFrequencies above the fundamental that are integer multiples of it. The 2nd harmonic = 2x fundamental (octave). The 3rd harmonic = 3x fundamental (perfect fifth + octave).
The fundamental is C2 (65.41 Hz). List the first six harmonics with their frequencies and approximate pitch names. Which harmonics form a major triad?