system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do equivalent notes played on different instruments sound different?

So if an A is 440hz, why does a piano playing an A sound different than a violin, a guitar, or someone’s voice making that same A 440 note? It’s obvious that the pitch is the same on each instrument but each instrument has a distinct sound. I’ve never heard an A on a piano and thought, is that a piano or a cello. Why can we distinguish between instruments?
gpt
Timbre is the word that describes the quality you're describing. While pitch is the frequency of the note, 440 Hz for A, the shape of the sound wave is not a perfect sine wave. The variation in the shape of the wave will contribute to the quality of the sound.