Timbre depends on sound order over time, not just spectral content.

Evidence

The onset phase for the reed stops is considerably more complicated since many more harmonics are present in each case. The fundamental for the hautbois and regal is evident first, and the second harmonic for the trompette. In all cases, the fundamental exhibits a frequency rise at onset during the first few cycles of reed vibration. The staggered times of entry of the higher harmonics form part of the acoustic timbral characteristic of that particular stop, the trompette having all harmonics present up to the 4 kHz upper frequency bound of the plot, the hautbois having all harmonics up to about 2.5 kHz, and the regal exhibiting little or no evidence (at this amplitude setting of the plot) of the fourth or eighth harmonics. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1449 (#exemplifies, via linked claim)

The note onset phase is particularly important to perceived timbre. Since listeners can reliably perceive the timbre of notes during the steadystate phase, it is clear that the offset phase is rather less important to the perception of timbre than the onset and steady-state phases. The onset phase is also more acoustically robust from the effects of the local environ­ ment in which the notes are played, since coloration of the direct sound by the first reflection (see Chapter 6) may occur after the onset phase is complete (and therefore transmitted uncolored to the listener). By defini­ tion the first reflection certainly occurs after part of the note onset has been heard uncolored. The onset phase is therefore a vital element and the off­ set phase an important factor in terms of timbre perception. — David Howard, Jamie Angus, coustics and Psychoacoustics, 1469 (#exemplifies, via linked claim)

Categorization

• XREF: connects to: An instrument’s normal attack transient is essential to its characteristic timbre; A note’s onset phase matters most for perceived timbre — David Howard, Jamie Angus, coustics and Psychoacoustics, 1469; Note onsets have staggered harmonic entry times that define each instrument’s timbre — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1449 (+5 more)

Broader Connections

• Reversing a sound changes perceived timbre without any spectral change. #exemplifies (0.95)
• Note onsets have staggered harmonic entry times that define each instrument’s timbre #exemplifies (0.88) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1449
• A note’s onset phase matters most for perceived timbre #exemplifies (0.80) — David Howard, Jamie Angus, coustics and Psychoacoustics, 1469