Timbre is a perceptual quality; spectrum is its physical correlate—they are related but not equivalent

Spectrum is a physical measurement: the distribution of energy across frequency at a given moment in time. Timbre is a perceptual attribute: the quality that allows a listener to distinguish two sounds of the same pitch, loudness, and duration—for example, a marimba from a violin. While timbre is strongly influenced by spectrum, it also depends on temporal evolution (attack characteristics, amplitude envelope), spectral flux, and context. The same static spectrum can sound different depending on how it was reached (attack shape). A common misconception treats spectrum and timbre as synonymous; correcting this is essential for understanding why spectral analysis alone is insufficient to predict perceived sound quality.

Examples

Two sounds with identical steady-state spectra but different attack envelopes are heard as different timbres (backwards piano vs. forward piano). Electric guitars with the same frequency response can sound radically different due to dynamic spectral evolution.

Assessment

Two recordings have identical FFT spectra measured during the sustain portion but very different attack times. Would listeners describe them as having the same timbre? Justify your answer using the distinction between spectrum and timbre.