The Everly Brothers are country

Country music

Country music is a popular American musical style that began in the rural Southern United States in the 1920s. It takes its roots from Western cowboy and folk music...

-influenced rock and roll

Rock and roll

Rock and roll is a genre of popular music that originated and evolved in the United States during the late 1940s and early 1950s, primarily from a combination of African American blues, country, jazz, and gospel music...

 performers, known for steel-string guitar playing and close harmony

Close harmony

Close harmony is an arrangement of the notes of chords within a narrow range. It is different from open harmony or voicing in that it uses each part on the closest harmonizing note , while the open voicing uses a broader pitch array expanding the harmonic range past the octave...

 singing. The brothers are the most successful US rock and roll duo on the Hot 100

Billboard Hot 100

The Billboard Hot 100 is the United States music industry standard singles popularity chart issued weekly by Billboard magazine. Chart rankings are based on radio play and sales; the tracking-week for sales begins on Monday and ends on Sunday, while the radio play tracking-week runs from Wednesday...

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This group was elected to the Rock & Roll Hall of Fame in 1986.
Don and Phil Everly are both guitarists and use a simple vocal harmony

Harmony

In music, harmony is the use of simultaneous pitches , or chords. The study of harmony involves chords and their construction and chord progressions and the principles of connection that govern them. Harmony is often said to refer to the "vertical" aspect of music, as distinguished from melodic...

 mostly based on parallel thirds. With this, each line can often stand on its own as a melody

Melody

A melody , also tune, voice, or line, is a linear succession of musical tones which is perceived as a single entity...

 line.