In music, a call and response is a succession of two distinct phrases usually written in different parts of the music, where the second phrase is heard as a direct commentary on or in response to the first. It corresponds to the call-and-response pattern in human communication and is found as a basic element of musical form, such as verse-chorus form, in many traditions.
In Sub-Saharan African cultures, call and response is a pervasive pattern of democratic participation--in public gatherings in the discussion of civic affairs, in religious rituals, as well as in vocal and instrumental musical expression.
It is this tradition that enslaved Africans brought with them to the New World and which has been transmitted over the centuries in various forms of cultural expression--in religious observance; public gatherings; sporting events; even in children's rhymes; and, most notably, in African-American music in its myriad forms and descendants including: soul, gospel, blues, rhythm and blues, rock and roll, funk and hip hop. Hear for example the recordings entitled "Negro Folklore from Texas State Prisons" collected by Bruce Jackson on Electra Records. Call and response is widely present in parts of the Americas touched by the trans-Atlantic slave trade. The tradition of call and response fosters dialogue and its legacy continues on today, as it is an important component of oral traditions. Both African-American Women Work Songs, African American work songs, and the work song in general use the call and response format often. It can also be found in the music of the Afro west indies Caribbean populations of Jamaica, Trinidad & Tobago, Bahamas, Barbados, Belize. and many nations of the diaspora especially that of south Americas Brazil.
In 1644, lining out - where one person sang a solo (a precentor) and others followed - is outlined by the Westminster Assembly for psalm singing in English churches. It has influenced popular music singing styles. Precenting the line was characterised by a slow, drawn-out heterophonic and often profusely ornamented melody, while a clerk or precentor (song leader) chanted the text line by line before it was sung by the congregation. Scottish Gaelic psalm-singing by precenting the line was the earliest form of congregational singing adopted by Africans in America.
It is common in folk traditions of choral singing of many people, especially in African musical cultures. In the West, it is most readily seen in the sea shanty, African-American work songs, African-American Women Work Songs, military cadences, Québecois folk songs, and the dance-songs of various European countries including France (particularly Brittany) and the Faroe Islands.
In Western classical music, call and response is known as antiphony. The New Grove Dictionary defines antiphony as "music in which an ensemble is divided in to distinct groups, used in opposition, often spatial, and using contrasts of volume, pitch, timbre, etc."
Gabrieli also contributed many instrumental canzonas, composed for contrasting groups of players:
Heinrich Schutz was one of the first composers to realise the expressive potential of the polychoral style in his "Little Sacred Concertos". The best known of these works is Saul, Saul, was verfolgst du mich? a vivid setting of the narrative of the Conversion of Paul as told in Acts 9 verses 3-4: "And as he journeyed, he came near Damascus: and suddenly there shined round about him a light from heaven. And he fell to the earth, and heard a voice saying unto him, Saul, Saul, why persecutest thou me?"
"The musical phrase on which most of the concerto is built is sounded immediately by a pair of basses":
This idea is "then taken up by the alto and tenor, then by the sopranos, and finally by the pair of violins as transition to the explosive tutti":
"The syncopated repetitions of the name Saul are strategically planted so that, when the whole ensemble takes them up, they can be augmented into hockets resounding back and forth between the choirs, adding to the impression of an enveloping space And achieving in sound something like the effect of the surrounding light described by the Apostle." 
In the following century, J.S. Bach featured antiphonal exchanges in his St Matthew Passion and the motets, such as Singet dem Herrn, BWV225. The New Grove Dictionary says that there are "genuine spatial effects in these works, but in general he used these divisions more because they made for increased sonority". The development of the classical orchestra in the late eighteenth and early nineteenth centuries exploited the dramatic potential of antiphonal exchanges between groups of instruments. An example can be found in the development section of the finale of Mozart's Symphony No. 41:
Even terser are the exchanges between wind and strings in the first movement of Beethoven's 5th Symphony. Here, the development culminates in a "singularly dramatic passage" consisting of a "strange sequence of block harmonies":
Twentieth century works that feature antiphonal exchanges include the second movement of Bartók's Music for Strings Percussion and Celesta (1936) and Michael Tippett's Concerto for Double String Orchestra (1938). One spectacular example from the 1950s is Karlheinz Stockhausen's Gruppen for Three Orchestras (1955-1957), which culminates in a "synchronized build-up of brass 'points' in the three orchestras ... leading to a climax of chord exchanges from orchestra to orchestra". When heard live, this piece creates a genuine sensation of music moving in space. "The combination of the three orchestras leads to great climaxes: long percussion solos, concertante trumpet solos, powerful brass sections, alternating and interpenetrating." 
The phenomenon of call and response is pervasive in modern Western popular music, as well, largely because Western music has been so heavily shaped by African contributions. Cross-over rhythm and blues, rock 'n' roll and rock music exhibit call-and-response characteristics, as well. The Who's song "My Generation" is an example:
Where call and response is most apparent in the secular music arena is in traditional and electric blues, where the most common 12-bar form is an AA'B pattern where the AA' is the call (repeated once with slight variation), and B is the response. But, each A and B part may itself consist of a short call and a short response, and those 2-bar calls and response may also be divided into 1-bar-each call-response pairs:
Note that each turnaround can be considered a call which the next A section is the response to.
A single leader makes a musical statement, and then the chorus responds together. American bluesman Muddy Waters utilizes call and response in one of his signature songs, "Mannish Boy" which is almost entirely leader/chorus call and response.
CALL: Waters' vocal: "Now when I was a young boy"
RESPONSE: (Harmonica/rhythm section riff)
CALL: Waters': "At the age of 5"
RESPONSE: (Harmonica/rhythm section riff)
Another example is from Chuck Berry's "School Day (Ring Ring Goes the Bell)".
CALL: Drop the coin right into the slot.
RESPONSE: (Guitar riff)
CALL: You gotta get something that's really hot.
RESPONSE: (Guitar riff)
CALL: Hey, I just met you
CALL: And this is crazy
This technique is utilized in Jepsen's song several times. While mostly in the chorus, it can also be heard in the breakdown (approximately 2:25) between the vocals ("It's hard to look right") and distorted guitar.
Part of the band poses a musical "question", or a phrase that feels unfinished, and another part of the band "answers" (finishes) it. In the blues, the B section often has a question-and-answer pattern (dominant-to-tonic).
An example of this is the Christmas song "Must Be Santa":
CALL: Who laughs this way, ho ho ho?
RESPONSE: Santa laughs this way, ho ho ho!
A similar question-and-answer exchange occurs in the movie Casablanca between Sam and the band in the song "Knock On Wood":
CALL: Who's got trouble?
RESPONSE: We've got trouble!
CALL: How much trouble?
RESPONSE: Too much trouble!