The bass guitar was invented in the 1930s as an alternative to the stand up double bass that was typically used to create sonorous resonance in jazz and blues, the precursors to rock and roll. The advent of the rock and roll sound, which included loud guitar licks and strums that would overpower the traditional bass lines, meant that the electric bass became a staple for many different artists.
The first widely successful basses, of the solid body model that we know today and which include bass guitar pickups in the composition, went on the market courtesy of Leo Fender in 1951.
Most commonly, a bass guitar will have four strings, tuned E-A-D-G. These strings are set to match the lowest four strings of the standard guitar, but are tuned one octave lower.
The bass was conceived as an electric instrument, meant to be amplified via bass guitar amps to give a rhythm and lower line feel to the music being performed. When performing acoustically or on quieter songs, artists would forego the bass altogether or go back to the stand up double bass model. This option was an expensive one, however, since large instruments such as the stand up bass continue to be the most costly and least portable (standard bass guitar cases are about half the size of double bass cases).
In the 1970s, Ernie Ball (a guitar developer well known for designing bass guitar accessories as well as accessories for other guitars) designed an acoustic bass that would accompany acoustic performances without drowning out the finer sound of the acoustic guitar.
These basses, like their electric counterparts, had a larger body than the acoustic guitars, which means that if you play one you will probably need one of the many bass guitar stands available. Bass guitar pickups for acoustic models are usually piezoelectric or magnetic. Bass guitar pickups are generally encouraged in the acoustic models as the low sounds mean that they are difficult to hear over other instruments when unamplified.
Although the four string, fretted bass is the most common type, these are by no means the only basses available. Musicians seeking to increase the range of sound in their music have the option of a five string and (although rarely used) even a six string bass.
In the five string model, a low B string is added above the E, while in the six string models a high C is added below the G. Acoustic basses with the added B string are often tuned differently in order to produce a sound that can be heard more readily while played.
Basses can also be purchased with no frets or with semi-fretting. Fretless basses are more akin to their stand-up originators and allow players more options in style of play, as well as a distinct sound created when the string is pressed directly on the wood. Semi-fretting models are very rare.
While bass guitars originally were created with 20 frets, modern basses will typically have 24 frets or more. This allows the artist to increase the range of sound created by te bass guitar strings.