Rhythm guitar is a guitar that is primarily used to provide rhythmic and harmonic accompaniment for a singer or for other instruments in an ensemble. The term refers to the use made of the instrument, not to its construction. The role of the rhythm guitar may be regarded as the complement to that of the lead guitar.
A rhythm guitar provides the pulse or rhythm for a song, and to provide harmony that supports the other instruments or voices, in contrast to the lead guitar, which provides melody. A rhythm guitar, therefore, is simply a musical concept which implies almost any guitar played in a way where it supplies the rhythm in conjunction with the bass guitarist and the drummer, usually in a rock band. For example, during solos, or "lead breaks", or during short "fills". Also, good rhythm guitar players often have melody in their playing, and lead guitarists are seldom ignorant of rhythm playing, and may use chords or strong rhythmic playing in their solos. A rhythm guitarist supplies the layer of rhythm on top of which the melody is either played using another instrument or sung by a person.
In rock music, the rhythm guitarist is typically expected to play a sequence of chords, called a chord progression, around which the song is constructed. Often this chordal accompaniment is simplified to a cluster of two or three notes, sometimes called a "riff", that is repeated. In metal, this is typically extended to more complex sequences consisting of a combination of chords, single notes and palm muted parts, while the more technical bands often play riffs which may use lead guitar techniques. In jazz or swing music, the rhythm guitarist is also expected to integrate a moving bass or counter-melody in his or her playing.
There is no defining line between a rhythm guitarist and lead guitarist, and if there is only one guitarist in the band, or if the songs require it, the guitarist may have to play lead and rhythm at different times. Thus, guitarist can play both rhythm and lead—it just depends on the parts that he or she plays in each song, and the capability of that guitarist.
Rhythm guitarists usually aim to generate a stronger tone as the harmonics of the band, in contrast to the lead guitarists' goal of producing a thin, trebly melody to cut through the sound of the rest of the band. As a result, rhythm and lead players may use different guitars. Rhythm guitarists may employ an electric acoustic guitar or a humbucker-equipped electric guitar for a richer and fatter output. Also, rhythm guitarists may used strings of a larger gauge than than those used by lead guitarists. However, while these may be practices, they are not neccessarily the rule and is subject to the style of the song and the preference of the individual guitarist.
There are a many specific styles of rhythm guitar:
-Big Band, as exemplified by Freddie Greene of the Count Basie Orchestra
-Western swing as played by Eldon Shamblin of the Bob Wills Orchestra