* Plucking or bowing the strings. The way that a string is plucked or bowed can produce different sounds. For example, plucking a string with a finger will produce a different sound than bowing it with a bow.
* Using different fingers or parts of the bow. Different fingers or parts of the bow can be used to create different sounds. For example, using the tip of the bow will produce a different sound than using the middle or the frog of the bow.
* Using different parts of the instrument. Different parts of the guitar or violin can be used to create different sounds. For example, playing on the higher strings of a guitar will produce a different sound than playing on the lower strings.
* Using different techniques. There are a number of different techniques that guitarists and violinists can use to create different sounds. Some of the most common techniques include vibrato, trills, and harmonics.
By combining these different techniques, guitarists and violinists can create a wide variety of different sounds. This allows them to express themselves musically in a variety of ways.