Temporal envelope alone, not spectral content, determines much of perceived timbre.

Evidence

Perhaps the most dramatic demonstration of context on timbre is to play a note backwards. A piano works especially well. As Murray Campbell and Clive Greated state in their book, The Musician’s Guide to Acoustics, if a piano is played backward the “instrument is transformed into a leaky old harmonium, although only the order of presentation of the sound has changed.” Indeed, the timbre as defined by the power spectrum has not changed, but the perceived timbre goes from a lovely grand piano to something rather unpleasant. … Sound that ramps up and suddenly ends can be turned into pulses that start abruptly and decay slowly, just by reversing them. This does not affect their spectral content, but they leave a very different impression. This is an easy experiment to try on your computer. — Eric J. Heller, Why You Hear What You Hear- An…, 2255

Categorization

• XREF: Connects to the broader ‘why we hear what we hear’ theme and to envelope/attack-decay discussions of instrument sound synthesis.
• CANDY: Reversing a piano note turns it into a ‘leaky old harmonium’ — fun, immediately tryable fact.
• SEED: An article about how reversing familiar sounds reveals what our ears actually use to identify instruments — the envelope as identity.