idea
Timbre
Timbre is the colour of a sound. It is why a violin and a flute playing the same A, equally loud, still sound like two different instruments. The main difference is in the harmonics: each instrument has its own balance of strong and weak ones. A bowed string has many strong upper harmonics, which makes it bright. A flute has fewer, so it sounds rounder. The beginning of the sound matters too. If you cut the attack off a recording, a piano and a trumpet become surprisingly hard to tell apart.