answer:The short answer is timbre, the “category for everything that cannot be labeled pitch or loudness”. Wikipedia – Timbre But I am very interested in hearing some more answers here, because my answer describes what is NOT timbre, rather than describing what IS timbre. And related to your question, I can never get my head around the idea that the sound of a whole orchestra (or any complex sound) can be played over a single loudspeaker using a single signal.