The bass guitar is a plucked string instrument that is a member of the guitar family. It has a longer neck and scale length than an electric or acoustic guitar and usually has four to six strings. Since the mid-1950s, it has largely replaced the double bass in popular music. The four-string bass guitar is usually tuned the same as the double bass. Bass pickups are generally attached to the body of the guitar and located beneath the strings, and they convert the vibrations of the strings into analogous electrical signals, which are passed as input to an instrument amplifier. Invented in the 1930s, the bass guitar has since undergone significant development and is now commonly used in various music genres, such as rock, funk, and jazz.