Rock and pop
Rock and pop rhythms
Most rhythms in rock and blues are based on 4/4 time with a backbeat; however, many variations are possible. A backbeat is a syncopated accentuation on the "off" beat. In a simple 4/4 rhythm these are beats 2 and 4. Emphasized back beat, a feature of some African styles, defined rhythm and blues recordings in the late 1940s and so became one of the defining characteristics of rock and roll and much of contemporary popular music.
While rhythm guitarists may in some cases perform a part composed by an arranger or by the composer of a song, they, like the other members of the rhythm section, are expected to be able to improvise or prepare their own part to fit a given song. This requires rhythm guitarists to have a good knowledge of how to use chord voicings, riffs, and fills that suit the style of a given song.
Rock and pop harmony
Harmonically, in rock music, the most common way to construct chord progressions is to play major and minor "triads", each comprising a root, third and fifth note of a given scale. An example of a major triad is C major, which contains the notes C, E and G. An example of a minor triad is the A minor chord, which includes the notes A, C and E. Interspersed are some four-note chords, which include the root, third and fifth, as well as a sixth, seventh or ninth note of the scale. The most common chord with four different notes is the dominant seventh chord, which include a root, a major third above the root, a perfect fifth above the root and a flattened seventh. In the key of C major, the dominant seventh chord is a G7, which consists of the notes G, B, D and F.
Three-chord progressions are common in earlier pop and rock, using various combinations of the I, IV and V chords, with the twelve-bar blues particularly common. A four chord progression popular in the 1950s is I-vi-ii-V, which in the key of C major is the chords C major, a minor, d minor and G7. Minor and modal chord progressions such as I-bVII-bVI (in the key of E, the chords E major, D major, C major) feature in popular music.
A power chord in E for guitar. This contains the notes E, B (a fifth above) and an E an octave higher.
In heavy metal music, rhythm guitarists often play power chords, which feature a root note and a fifth above, or with an octave doubling the root. There actually is no third of the chord. Power chords are usually played with distortion.
One departure from the basic strummed chord technique is to play arpeggios, i.e. to play individual notes in a chord separately. If this is rapidly done enough, listeners will still hear the sequence as harmony rather than melody. Arpeggiation is often used in folk, country, and heavy metal, sometimes in imitation of older banjo technique. It is also prominent in 1960s pop, such as The Animals' "House of the Rising Sun", and jangle pop from the 1980s onwards. Rhythm guitarists who use arpeggio often favor semi-acoustic guitars and twelve string guitars to get bright, undistorted "jangly" sound.
The Soukous band TPOK Jazz additionally featured the unique role of mi-solo, (meaning "half solo") guitarist, playing arpeggio patterns and filling a role "between" the lead and rhythm guitars.
In some cases, the chord progression is implied with a simplified sequence of two or three notes, sometimes called a "riff". That sequence is repeated throughout the composition. In heavy metal (or just "metal") music, this is typically expanded to more complex sequences comprising a combination of chords, single notes and palm muting. The rhythm guitar part in compositions performed by more technically oriented bands often include riffs employing complex lead guitar techniques. In some genres, especially metal, the audio signal from the rhythm guitar's output is often subsequently heavily distorted by overdriving the guitar's amplifier to create a thicker, "crunchier" sound for the palm-muted rhythms.
Interaction with other guitarists
In bands with two or more guitarists, the guitarists may exchange or even duplicate roles for various songs or several sections within a song. In those with a single guitarist, the guitarist may play lead and rhythm at numerous times or simultaneously, by overlaying the rhythm sequence with a lead line.
Crossover with keyboards
The availability of electronic effects units such as delay pedals and reverb units enables electric guitarists to play arpeggios and take over some of the role of a synthesizer player in performing sustained "pads". Those serve as sonic backgrounds in modern pop. Creating a pad sound differs from usual rhythm guitar roles in that it is not rhythmic. Some bands have a synthesizer performer play pads. In bands without a synth player, a guitarist can take over this role.
Replacing lead guitar
Some rhythm techniques cross over into lead guitar playing. In guitar-bass-and-drums power trios guitarists must double up between rhythm and lead. For instance Jimi Hendrix combined full chords with solo licks, double stops and arpeggios. In the 2010s, "looping pedals" are used to record a chord sequence or riff over which musicians can then play the lead line, simulating the sound achieved by having two guitarists.
Rhythm guitarists usually aim to generate a stronger rhythmic and chordal sound, in contrast to the lead guitarists' goal of producing a sustained, high-pitched melody line that listeners can hear over the top of the band. As a result, rhythm and lead players may use different guitars and amplifiers. Rhythm guitarists may employ an electric acoustic guitar or a humbucker-equipped electric guitar for a richer and fatter output. Also, rhythm guitarists may use strings of a larger gauge than those used by lead guitarists. However, while these may be practices, they are not necessarily the rule and is subject to the style of the song and the preference of the individual guitarist.
While rhythm guitarists in metal bands use distortion effects, they tend to use less of the modulation effects such as flangers used by lead guitar players. Whereas the lead guitarist in a metal band is trying to make their solo tone more prominent, and thus uses a range of colorful effects, the rhythm guitarist is typically trying to provide a thick, solid supporting sound that blends in with the overall sound of the group. In alternative rock and post punk bands, however, where the band is trying to create an ambient soundscape rather than an aggressive Motörhead-style "Wall of Sound", the rhythm guitarist may use flanging and delay effects to create a shimmering background.