Final answer:
A guitar, typically with 6 strings, is a type of chordophone that creates sound through the vibration of strings. It can be classified as a stringed instrument in music theory, and it comes in various types such as classical or electric.
Step-by-step explanation:
The musical instrument that usually has 6 strings is a guitar. A guitar is a chordophone, which is a category of musical instruments in ethnomusicology. It produces sound through the vibrations of its strings, typically made of nylon or steel. When a musician plucks or strums the strings, they vibrate and produce sound waves. These waves resonate within the body of the guitar, amplifying the sound. The vibration of the strings creates standing waves, with nodes that do not move and antinodes that experience the greatest amplitude of motion.
Guitars can exist as acoustic, which have a hollow body that resonates the sound, or electric, which use electronic amplification to produce sound. In addition to acoustic and electric types, there are classical guitars with nylon strings and steel-string guitars, both of which are commonly seen in various music genres.
When looking at different kinds of instruments and how they produce sound, the guitar is grouped with stringed instruments. In a music theory class, other categories you might learn about include wind instruments, woodwind instruments, brass instruments, and percussion instruments.