A-side and B-side

The first sound recordings were produced in the late 19th century using cylinder records, which held approximately two minutes of audio stored upon a single round surface. One-sided disc records made of shellac co-existed with cylinders and had a similar capacity. In 1908, Columbia Records introduced double-sided recordings with one selection on each side in European markets. Although cylinders and discs remained comparable and competitive for a time (both media would be able to hold between three and four minutes of sound by 1910), ultimately, discs superseded the cylinder format, rendering it obsolete by 1912, largely due to its shorter play times.

Record producers did not initially have reason to value either side of double-sided records as being more important than the other. There were no record charts until the 1930s, and most radio stations did not broadcast recorded music until the 1950s, when the Top 40 radio format overtook full-service network radio). In June 1948, Columbia Records introduced the modern 33​¹⁄₃ rpm long-playing (LP) microgroove vinyl record for commercial sales, and its rival RCA Victor, responded the next year with the seven-inch 45 rpm vinylite record, which would quickly replace the 78 for single record releases. The term "single" came into popular use with the advent of vinyl records in the early 1950s. During this period, most record labels would designate one song an A-side and the other a B-side at random. (All records have specific identifiers for each side in addition to the catalog number for the record itself; the "A" side would typically be assigned a sequentially lower number.) Under this random system, many artists had so-called "double-sided hits", where both songs on a record made one of the national sales charts (in Billboard, Cashbox, or other magazines), or would be featured on jukeboxes in public places.

Conventions shifted in the early 1960s, at which point record companies started assigning the song they wanted radio stations to play to side A, as 45 rpm single records ("45s") dominated most markets in terms of cash sales in comparison to albums, which did not fare as well financially. Throughout the decade the industry would slowly shift to an album-driven paradigm for releasing new music; it was not until 1968 that the total production of albums on a unit basis finally surpassed that of singles in the United Kingdom.[2] In the late 1960s, stereo versions of pop and rock songs began appearing on 45s. However, since the majority of the 45s were played on AM radio stations that were not yet equipped for stereo broadcast, stereo was not a priority. Nevertheless, FM rock stations did not like to play monaural content, so the record companies adopted a protocol for promotional recordings for disc jockeys with the mono version of a song on one side and a stereo version of the same song on the other. By the early 1970s, album sales had increased and double-sided hit singles had become rare. Record companies started to use singles as a means of promoting albums; they frequently placed album tracks that they wished to promote on side A and less accessible, non-album, instrumental songs on side B. In order to ensure that radio stations played the side that the record companies wanted to promote, they often marked one side of a record's label as a "plug side."

The distinction between the two sides became less meaningful after the introduction of cassettes and compact disc singles in the late 1980s when 45 rpm vinyl records began to decline. At first, cassette singles would often have one song on each side, matching the arrangement of vinyl records. Eventually though, cassette maxi-singles containing more than two songs became more popular. As the one-sided audio compact disc became the dominant recording medium in the late 1990s, cassettes began vanishing and the A-side/B-side dichotomy became virtually extinct. The term “B-side” continued to enjoy varying levels of use in reference to the "bonus" tracks or "coupling" tracks on a CD single.

In the last few decades, the industry has largely shifted away from physical media towards digital music distribution formats, further diminishing the relevance of terminology or marketing strategies based on “sides.” Today, companies label non-album songs and tracks deemed less desirable or marketable using terms such as "unreleased,”, "bonus,”, "non-album,” "rare,” "outtakes,” or "exclusive.” Such material is sometimes grouped for downloading or streaming together into “bonus” or “extended” versions of an artist's albums on digital music platforms.

B-side songs may be released on the same record as a single to provide extra "value for money". There are several types of material commonly released in this way, including a different version (e.g., instrumental, a cappella, live, acoustic, remixed version or in another language), or, in a concept record, a song that does not fit into the story line.

Additionally, it was common in the 1960s and 1970s for longer songs, especially by soul, funk, and R&B acts, to be broken into two parts for single release. Examples of this include Ray Charles's "What'd I Say", the Isley Brothers' "Shout", and a number of records by James Brown, including "Papa's Got a Brand New Bag" and "Say It Loud - I'm Black and I'm Proud". Typically, "part one" would be the chart hit, while "part two" would be a continuation of the same performance. A notable example of a non-R&B hit with two parts was the single release of Don McLean's "American Pie". With the advent of the 12-inch single in the late-1970s, the part one/part two method of recording was largely abandoned. Modern day examples are Fall Out Boy's EP, My Heart Will Always Be The B-Side To My Tongue, or My Chemical Romance's The Black Parade: The B-Sides.

Since both sides of a single received equal royalties, some composers deliberately arranged for their songs to be used as the B-sides of singles by popular artists. This became known as the "flipside racket". Similarly, it has also been alleged that owners of pirate radio stations operating off the British coast in the 1960s would buy the publishing rights to the B-sides of records they expected to be hits, and then plug the A-sides in the hope of driving up sales and increasing their share of the royalties.

Occasionally, the B-side of a single would become the more popular song. This sometimes occurred because a DJ preferred the B-side to its A-side and played it instead. Some examples include "I Will Survive" by Gloria Gaynor (originally the B-side of "Substitute"), "Ice Ice Baby" by Vanilla Ice (originally the B-side of "Play That Funky Music"), "I'll Be Around" by the Spinners (originally the B-side of "How Could I Let You Get Away") and "Maggie May" by Rod Stewart (originally the B-side of "Reason to Believe"). Probably the most well-known of these, however, is "Rock Around the Clock" by Bill Haley & His Comets (originally the B-side of "Thirteen Women (And Only One Man in Town))".

The song "How Soon Is Now?" by the Smiths started out as the extra track on the 12-inch of William, It Was Really Nothing but later gained a separate release as an A-side in its own right, as did Oasis's "Acquiesce", which originally appeared as a B-side to "Some Might Say" in 1995, but gained subsequent release in 2006 as part of an EP to promote their forthcoming compilation album, Stop the Clocks. Feeder in 2001 and 2005 had the B-sides "Just a Day" from "Seven Days in the Sun", and "Shatter" from "Tumble and Fall" released as A-sides after fan petitions and official website and fansite message board hype, and both charted at No. 12 and No. 11 in the UK. In 1986, the first single from XTC's record Skylarking, "Grass", was eclipsed in the United States by its B-side, "Dear God" – so much so that the record was almost immediately re-released with one song ("Mermaid Smiled") removed and "Dear God" put in its place, becoming one of the band's better-known hits.

On many reissued singles, the A- and B-sides are two hit songs from different albums that were not originally released together, or were by completely different artists, altogether. These were often made for the jukebox, as one record with two popular songs on it would make more money, or to promote an artist to the fans of another. For example, in 1981 Kraftwerk released their new single "Computer Love" coupled with the B-side "The Model", from their 1978 LP The Man-Machine. With synthpop increasingly dominating the UK charts, the single was re-released with the sides reversed. In early 1982 "The Model" reached number one.

A "double A-side" or "AA-side" is a single where both sides are designated the A-side, with no designated B-side; that is, both sides are "hits" or prospective hit songs and neither side will be promoted over the other. In 1949, Savoy Records promoted a new single by one of its artists, Paul Williams' "House Rocker" and "He Knows How to Hucklebuck", as "The New Double Side Hit – Both Sides "A" Sides".[3] In 1965, Billboard reported that due to a disagreement between EMI and John Lennon about which side of the Beatles' "We Can Work It Out" and "Day Tripper" single should be considered the A-side and receive the plugging, "EMI settled for a double-side promotion campaign—unique in Britain."[4] They continued to use the format for the release of the singles "Eleanor Rigby" and "Yellow Submarine" in 1966, followed by "Strawberry Fields Forever" / "Penny Lane" in 1967 and "Something" / "Come Together" in 1969. Other groups followed suit, notably the Rolling Stones in early 1967 with "Let's Spend the Night Together" / "Ruby Tuesday" as a double-A single.

A double A-sided single is often confused with a single where both sides, the A and the B, became hits. Although many artists in the late 1950s and early 1960s like Elvis Presley, the Everly Brothers, Fats Domino, Ricky Nelson, the Beach Boys, Brenda Lee, and Pat Boone, routinely had hit singles where both sides of the 45 received airplay, these were not double A-sides. The charts below tally the instances for artists' singles where both sides were hits, not where both sides were designated an A-side upon manufacture and release. For instance "Don't Be Cruel", the B-side of "Hound Dog" by Elvis Presley, became as big a hit as its A-side even though "Don't Be Cruel" was not the intended A-side when released in 1956. Reissues later in the 1960s (and after the Beatles' "Day Tripper"/"We Can Work It Out") listed the single with both songs as the A-side. Also, for Cliff Richard's 1962 "The Next Time"/"Bachelor Boy", both sides were marketed as songs with chart potential, albeit with "Bachelor Boy" pressed as the B-side.

In the UK, before the advent of digital downloads, both A-sides were accredited with the same chart position, as the singles' chart was compiled entirely from physical sales. In the UK, the biggest-selling non-charity single of all time was a double A-side, Wings' 1977 release "Mull of Kintyre"/"Girls' School", which sold over two million copies. It was also the UK Christmas No. 1 that year, one of only two occasions on which a double A-side has topped that chart, the other being Queen's 1991 re-release of "Bohemian Rhapsody" with "These Are the Days of Our Lives".[5] Nirvana released "All Apologies" and "Rape Me" as a double A-side in 1993, and both songs are accredited as a hit on both the UK Singles Chart,[6] and the Irish Singles Chart.[7]

Queen released their first double-A single, "Killer Queen"/"Flick of the Wrist", in 1974. "Killer Queen" became a hit, while "Flick of the Wrist" was all but ignored for lack of promotion. Three years later, they released "We Are the Champions" with "We Will Rock You" as a B-side. Both sides of the single received much radio airplay (often one after the other), which led to them sometimes being referred to as a double A-side. In 1978 they released "Fat Bottomed Girls"/"Bicycle Race" as a double A-side; that time both sides of the single became hits.

Occasionally double-A-sided singles were released with each side targeting a different market. During the late 1970s, for example, Dolly Parton released a number of double-A-sided singles, in which one side was released to pop radio, and the other side to country, including "Two Doors Down"/"It's All Wrong, But It's All Right" and "Baby I'm Burnin'"/"I Really Got the Feeling". In 1978, the Bee Gees also used this method when they released "Too Much Heaven" for the pop market and the flip side, "Rest Your Love on Me", which was aimed toward country stations.

Many artists continue to release double A-sided singles outside of the US where it is seen as more popular. Examples of this include Oasis's "Little by Little"/"She Is Love" (2002), Bloc Party's "So Here We Are"/"Positive Tension" (2005) and Gorillaz's "El Mañana"/"Kids with Guns" (2006).

Artists having the most US double-sided singles on which each side charted in the US Hot 100, according to Billboard:[8]

• Perry Como (12) and Nat King Cole (19) both had additional double-sided singles on Billboard's pre-1955 charts.[9]

Artists having the most US double-sided singles on which each side reached the Billboard Top 40, according to Billboard:[8]

On vinyl, double A-sided singles had one song on either side of the record, while double B-sides contained two songs on the same side (on the B-side, making three songs in all). When such singles were introduced in the 1970s, the popular term for them was "maxi single", though this term is now used more ambiguously for a variety of formats. For some people these records would not quite qualify as EPs, for those generally have four songs on a 45.

Genesis's 1978 7-inch single "Many Too Many" featured two B-sides, "The Day the Light Went Out" and "Vancouver", both of them being outtakes from the ...And Then There Were Three... album. There was no 12-inch equivalent. The band released two 7-inch singles with three tracks apiece, Spot the Pigeon and 3X3 (also known as "Paperlate"), which were explicitly marked as EPs. "Spot the Pigeon" was also available in a 12-inch version, and also subverted this format a bit, by having two tracks on the A-side and one track on the B-side. The B-side, "Inside and Out", was also considered the selling point of the EP, being Steve Hackett's last contribution to the band, and remains a favorite of many fans.

Paul McCartney's 1980 single "Coming Up" had a studio version of the song on the A-side, while the B-side contained two songs, a live version of "Coming Up" and a studio instrumental called "Lunchbox/Odd Sox".

Iron Maiden's 1980 7-inch single "Sanctuary" was a re-recording of a song that had been given for use on the Metal For Muthas compilation the previous year. The recording was made during the Iron Maiden sessions but was left off the UK version of that album, and was then put out as a single. To help compensate fans who had specifically bought Metal for Muthas for the track, the "Sanctuary" single had two live B-sides which were deliberately selected to be non-album tracks—"I've Got The Fire" (a cover of the Montrose song) and "Drifter". A studio recording of "Drifter" (featuring Adrian Smith instead of Dennis Stratton) appeared on their next album, Killers, and a studio version of "I've Got The Fire" featuring Bruce Dickinson appeared on the B-side of "Flight of Icarus" a few years later. At the time this single was released they were the first live Iron Maiden tracks released (though more would follow), and it remains the only officially released recording of "I've Got The Fire" with Paul Di'Anno on vocals.

The singles from U2's album The Joshua Tree were released with two B-side songs each, which were pressed at 33​¹⁄₃ rpm. Versions for jukeboxes included only one of those songs, which played at 45 rpm.

The UK 7-inch single of "Love Shack" by The B-52's was released with live versions of "Planet Claire" and "Rock Lobster" on the B-side, which plays at 33​¹⁄₃ rpm. The follow-up "Roam" followed suit, including live versions of "Whammy Kiss" and "Dance This Mess Around" on the B-side playing at 33​¹⁄₃ rpm.

The Rolling Stones released "Brown Sugar" from their album Sticky Fingers in May 1971. While the American single featured only "Bitch" as the B-side, the British single added a third track, a live rendition of "Let It Rock" (the Chuck Berry classic) recorded at the University of Leeds during their 1971 tour of the UK.

The concept of the B-side has become so well known that many performers have released parody versions, including:

• The 1988 single "Stutter Rap (No Sleep til Bedtime)" by parody band Morris Minor and the Majors featured a B-side titled "Another Boring 'B'-side".
• Little Nell's EP The Musical World of Little Nell (Aquatic Teenage Sex & Squalor) claimed to be the world's first triple B-side.
• Parody band Bad News recorded a video B-side for the VHS version of their single "Bohemian Rhapsody", titled "Every Mistake Imaginable", in which the band discusses that they have to record an extra three minutes of footage for the single to be eligible for the charts.
• Tracey Ullman's hit "They Don't Know" was backed in the UK by a song entitled "The B Side" and featured Ullman in a variety of comic monologues, many of which bemoaned the uselessness of B-sides. (The US release used the album's title track, "You Broke My Heart in 17 Places", as the B-side.)
• Harry Enfield's 1988 novelty single "Loadsamoney (Doin' Up the House)" features a B-side entitled "The B Side" in which Enfield and Paul Whitehouse, in character as Loadsamoney and Lance respectively, discuss the creation of a B-side for their record.
• Paul and Linda McCartney's B-side to Linda McCartney's "Seaside Woman" (released under the alias Suzy and the Red Stripes) was a song called "B-Side to Seaside".
• The single "O.K.?", from the soundtrack album of the TV series Rock Follies of '77, contained a song called "B-Side?" which featured Charlotte Cornwell tunelessly singing about the fact that she is not considered good enough to sing an A-side.
• The B-side of the single "They're Coming to Take Me Away, Ha-Haaa!" by Napoleon XIV was called "!aaaH-aH, yawA eM ekaT oT gnimoC er'yehT" and the singer billed as "Noelopan VIX". It was the A-side played in reverse; in fact, most of the label affixed to that B-side was a mirror image of the front label (as opposed to being spelled backwards), including the letters in the "WB" shield logo.
• Blotto's 1981 single "When the Second Feature Starts" features "The B-Side", a song about how bad B-sides are compared to A-sides.
• Love and Rockets' novelty side project the Bubblemen released only one single in 1988, "The Bubblemen Are Coming" coupled with "The B-Side", which is a field recording of bees.
• The Wall of Voodoo 1982 12-inch EP Two Songs by Wall of Voodoo has the 10-minute joke track "There's Nothing on This Side" on the B-side.
• Metric released in 2008 a single entitled "Help, I'm Alive", with a B-side "Help, I'm a B-Side".
• Three Dog Night's 1973 single "Shambala" featured "Our 'B' Side", about the group wishing it could be trusted to write their own songs for single release. It is the only Three Dog Night single written and produced by the whole group, and features family members on background vocals.
• Dickie Goodman's 1974 release "Energy Crisis '74" featured "The Mistake" as the B-side, which was simply a false start of the A-side, with Goodman saying, "Mr. President, the crisis...", followed by two minutes of silence. (It was literally a mistake: the intended B-side was an instrumental called "Ruthie's Theme".[10] However, when Goodman realized the factory had stamped a number of the botched pressings, he simply placed the full version of "Energy Crisis '74" on the other side, and released the records anyway.)
• The Pearl Harbor and the Explosions song "You Got It" was backed by "Busy Little B Side", also found on the Warner Bros. two-LP sampler, Troublemakers.
• The B-side of B. A. Robertson's 1979 single "Goosebumps" is entitled "The B-Side" and contains lyrics from the song's point of view. The lyrics describe the song as being "the back of a hit" and "real popular after the war", which can be said to relate to the dominance of the 45 rpm single after World War II, and the change of significance of the A-side and the B-side after this time. This track also opens side two of Robertson's album Initial Success.
• One of the B-sides from Lenny Kravitz's single "Heaven Help" is called "B Side Blues" and documents the sheer boredom of him being under a lot of pressure from his record company to write more successful material.
• Kaiser Chiefs released a 7-inch single of "You Can Have It All" that featured a blank B-side. Parodying their hit record I Predict A Riot, the label on this blank side suggested it contained the track "I Predict Some Quiet".
• The B-side of George Harrison's "Dark Horse", "I Don't Care Any More", starts with a recitative marking the casual nature of the performance, reflected in Harrison's spoken introduction before the first verse: "OK, here we go, fellas / We got a B-side to make, ladies and gentlemen so we better get on with it."
• The cassette release of In God We Trust, Inc. by the Dead Kennedys featured a blank B-side, the entire album being on Side A. Printed on Side B was the explanation "Home taping is killing record industry profits! We left this side blank so you can help."[11]

The term "b/w", an abbreviation of "backed with", is often used in listings to indicate the B-side of a record. The term "c/w", for "coupled with", is used similarly.[12]