Bass guitar
A bass guitar is used to fill in the bottom end of music in many bands, and fills in the role that had tradionally been played by the Double Bass (often called a standup or upright bass) in orchestras and bluegrass music. The standard tuning used by most musicians for the 4-string bass guitar is identical to the standard tuning of the double bass, the four strings being exactly one octave below the bottom (lowest notes, highest vertically) strings of a six-string guitar.
Bass guitars became quite popular with the introduction of the Fender P-bass. Although many modern bass guitar designs have favored the P-bass' fretted electric style, recent decades have seen the acoustic bass guitar and the (electric, solid-body) fretless bass guitar gain in popularity.
Tuning
Traditionally, the 4-string bass guitar is tuned, from lowest to highest (pitch), in E, A, D and G. Some five-string bass guitars have an additional higher (pitched) string tuned to B, analogous to the fifth string of a tradional (six-string) guitar, but most add a fifth string below the low E for a B string that is lower in pitch than most other stringed instruments.
Bass lines/Beat patterns
The bass guitar often emphasises the first and third note of each measure, while the drums emphasise beats two and four. The simplest patterns played on a bass guitar occur in country music, with the traditional quarter note pattern with emphasis on the first and third notes, usually the root of the chord, and less emphasis on beats two and four, usually the fifth note or an octive of the root chord, both of which are played at a lower note. In music notation, this would be:
| I - V - I -V | or | VIII - I - VIII - I |
In many blues tunes and rock-and-roll music, the bass line for each chord will include the first, third and fifth notes of the chord, played like so for a single measure:
| I - III - V - III | Beat pattern for many blues and rock songs -1 measure
For songs in which the chord remains the same for two measures, this pattern is often turned into a longer beat pattern which walks up and back down like this:
| I - III - V - VI - VIII - VI - V - III |, which in the key of G for example would be:
| G - B - D - E - G - E - D - B |