How do pizzicato and tremolo create different sounds on string instruments?

In the context of instrumentation, pizzicato and tremolo are distinct playing techniques that allow string players to alter the timbre and character of their instruments.12

• Pizzicato: This technique involves plucking the strings with the fingers instead of using a bow. Because the string is set into motion by a direct pluck rather than continuous friction, it produces a shorter, more percussive sound that emphasizes different overtones compared to bowed notes.321
• Tremolo: This technique is defined by the quick, rapid reiteration of the same tone. By repeatedly and rapidly moving the bow back and forth, the player creates a shimmering or intense sustained effect that differs significantly from the decay of a plucked note.2

These techniques are essential for composers, particularly in settings like the string quartet, where varying playing methods are used to achieve a wide range of expressive colors and textures without changing instruments.2