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Harmonic SeriesWhat Is a Musical SoundRegisterPitch

Play one pitch on a piano and you get a ping; on a violin, a wail; on a flute, a breath. Same frequency, same loudness, same duration — the only thing left to name is timbre. Of the four properties of a tone, it is the one that cannot be plotted on a single axis.

Three things determine timbre

One: how strong each partial is. A tone is a fundamental plus a stack of partials. Their relative strengths draw the outline of the timbre: strong upper partials sound bright, sharp, metallic; suppressed upper partials sound round, soft, muffled.

Two: the attack envelope. How the sound arrives and leaves. Three stretches matter:

• Attack: how long it takes to climb from silence to full level. Very short reads as percussion (piano,

drums); longer reads as blowing or bowing (flute, strings).

• Decay: the shape of the fall from the peak. A fast fall gives articulation; a slow one gives continuity.
• Release: how the tail disappears once you let go.

Three: the resonator and how it radiates. The same excitation through a different body changes everything. A piano's cast-iron frame and soundboard, a violin's arched belly, an organ's metal and wooden pipes — all are ways of choosing a shape to amplify and filter the vibration.

Diagram: three attack envelopes

Why the word "waveform" is useful

Draw one cycle of a vibration as a curve and you have a waveform. A few basic shapes correspond to particular partial patterns:

Real instrument timbres are mixtures of these shapes that change over time, and the change is fastest during the attack — which is why a single static curve can never describe a timbre completely.

Listen: the control case for timbre

Every tone below comes from the same in-page synth and therefore has exactly the same timbre. Treat it as a baseline: play the same notes on an instrument and everything you hear differently is timbre.

How timbre is used in writing

• A change of narrator. Give the theme to another instrument and you have a new speaker without altering a single note of structure or melody.
• Blending into a third colour. Two instruments in unison fill in each other's partials and produce a sound that is neither. Mixing woodwind with strings is the most common trick in orchestration.
• Register is timbre. One instrument changes character drastically across register, so "which instrument" and "which register" are really the same decision.

Common misconceptions

• "Timbre is subjective, so it cannot be discussed." The impression is subjective; the causes are entirely objective, since both partial content and envelope can be measured.
• "Timbre means the maker's name on the instrument." One instrument changes timbre by register, dynamic and technique. The maker is only one variable.
• "Timbre has nothing to do with pitch." It does. Change the pitch and every partial's absolute frequency changes with it, which changes how the resonator responds.
• "Sine waves sound best." They simply carry the least information. A melody on pure sine tones sounds bland precisely because nothing distinguishes one from another.

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Sources

• 音色的三个物理构成（分音构成、起音包络、共鸣体特性）属音乐声学通行表述
• 波形（正弦 / 方波 / 锯齿波）与分音构成的关系属信号与声学常识

Used for fact-checking only; all prose is original.