A440

A440 refers to the tuning standard where the musical note A above middle C vibrates at 440 hertz, meaning it produces 440 sound waves per second. This frequency serves as a reference point for tuning musical instruments, ensuring that they sound harmonious when played together. Established in the early 20th century, A440 is widely used globally and provides consistency in musical performances and recordings. Essentially, it helps musicians and orchestras stay in tune by providing a common pitch standard.