The bass guitar, electric bass or simply bass is the lowest-pitched member of the guitar family. It is a plucked string instrument similar in appearance and construction to an electric or acoustic guitar, but with a longer neck and scale length. The bass guitar most commonly has four strings, though five- and six-stringed models are also relatively popular, and bass guitars with even more strings or courses have been built. Since the mid-1950s, the bass guitar has largely come to replace the double bass in popular music due to its lighter weight, the inclusion of frets in most models, and, most importantly, its design for electric amplification. This is also because the double bass is acoustically compromised for its range in that it is scaled down from the optimal size that would be appropriate for those low notes.