Background: Wishbone Ash are a British rock band who achieved success in the early and mid-1970s. Their popular albums included Wishbone Ash (1970), Pilgrimage (1971), Argus (1972), There's the Rub (1974), and New England (1976). Wishbone Ash are noted for their extensive use of the harmony twin lead guitar format which had been attracting electric blues bands since Jeff Beck and Jimmy Page had played together in the Yardbirds in 1966. Their contributions helped Andy Powell and Ted Turner to be voted "Two of the Ten Most Important Guitarists in Rock History" (Traffic magazine 1989), and to appear in the "Top 20 Guitarists of All Time" (Rolling Stone).
Context: Turner was replaced by bassist and vocalist John Wetton, formerly of Family, King Crimson, Roxy Music, Uriah Heep and UK. Number the Brave was released in April 1981 and featured Wetton's lead vocals on just one song, although during album sessions he had offered songs such as "Here Comes the Feeling" that would eventually sell millions when released on Asia's 1982 debut album. Wetton did not continue with Wishbone Ash beyond the album sessions and rejoined Asia.  Wetton was replaced on the Number the Brave tour by the former Uriah Heep bassist Trevor Bolder. Also joining the band was female backing vocalist, Claire Hamill, who had sung on both the Just Testing and Number the Brave albums. In 1982, after Hamill's departure, the band experimented with heavy metal on the Twin Barrels Burning album. It became the highest charting Wishbone Ash album in years (UK #22).  Bolder left the group to rejoin Uriah Heep in 1983, to be replaced by bassist/vocalist Mervyn Spence (ex-Trapeze). The group continued with a heavy metal side on 1985's Raw to the Bone, which became the first Wishbone Ash album not to make the charts. Not long after, Wisefield left after serving as guitarist in the band for eleven years, going on to a varied career that would include work with Tina Turner, Joe Cocker, Roger Chapman, Jeff Wayne and the Queen musical We Will Rock You. He was replaced by Jamie Crompton, who in turn was succeeded briefly by Phil Palmer. Early in 1986, Mervyn Spence quit as well, to be replaced by ex-Kinks bassist Andy Pyle.
Question: What was the instability about this timeframe?
Answer: Not long after, Wisefield left after serving as guitarist in the band for eleven years,

Question:
Yelberton Abraham Tittle Jr. (October 24, 1926 - October 8, 2017), better known as Y. A. Tittle, was a professional American football quarterback. He played in the National Football League (NFL) for the San Francisco 49ers, New York Giants, and Baltimore Colts, after spending two seasons with the Colts in the All-America Football Conference (AAFC). Known for his competitiveness, leadership, and striking profile, Tittle was the centerpiece of several prolific offenses throughout his seventeen-year professional career from 1948 to 1964. Tittle played college football for Louisiana State University, where he was a two-time All-Southeastern Conference (SEC) quarterback for the LSU Tigers football team.
A photo of a dazed Tittle in the end zone taken by Morris Berman of the Pittsburgh Post-Gazette on September 20, 1964, is regarded among the most iconic images in the history of American sports and journalism. Tittle, in his 17th and final season, was photographed helmet-less, bloodied and kneeling immediately after having been knocked to the ground by John Baker of the Pittsburgh Steelers and throwing an interception that was returned for a touchdown at the old Pitt Stadium. He suffered a concussion and cracked sternum on the play, but went on to play the rest of the season.  Post-Gazette editors declined to publish the photo, looking for "action shots" instead, but Berman entered the image into contests where it took on a life of its own, winning a National Headliner Award. The photo was published in the October 2, 1964, issue of Life magazine. It is regarded as having changed the way that photographers look at sports, having shown the power of capturing a moment of reaction. It became one of three photos to hang in the lobby of the National Press Photographers Association headquarters, alongside Raising the Flag on Iwo Jima and the Hindenburg disaster. A copy now hangs in the Pro Football Hall of Fame.  After at first having failed to see the appeal of the image, Tittle eventually grew to embrace it, putting it on the back cover of his 2009 autobiography. "That was the end of the road," he told the Los Angeles Times in 2008. "It was the end of my dream. It was over." Pittsburgh player John Baker, who hit Tittle right before the picture was taken, ran for sheriff in his native Wake County, North Carolina in 1978, and used the photo as a campaign tool. He was elected and went on to serve for 24 years. Tittle also held a fundraiser to assist Baker in his bid for a fourth term in 1989.
Answer this question using a quote from the text above:

What year was the famous photo taken?

Answer:
on September 20, 1964,

Problem: Background: A boy band (or boyband) is loosely defined as a vocal group consisting of young male singers, usually in their teenage years or in their twenties at the time of formation, singing love songs marketed towards young women. Being vocal groups, most boy band members do not play musical instruments, either in recording sessions or on stage, making the term something of a misnomer. However, exceptions do exist. Many boy bands dance as well as sing, usually giving highly choreographed performances.
Context: The earliest forerunner of boy band music began in the late 19th century as a cappella barbershop quartets. They were usually a group of males and sang in four-part harmonies. Barbershop quartets were popular into the earlier part of the 20th century. A revival of the male vocal group took place in the late 1940s and 1950s with the use of doo-wop music. Doo-wop bands sang about topics such as love and other themes used in pop music. The earliest traces of boy bands were in the mid-1950s although the term boy band was not used. African American vocal group The Ink Spots was one of the first of what would now be called boy bands. The term boy band was not established until the late 1980s as before that they were called male vocal groups or "hep harmony singing groups".  Although generally described as a rock band, the highest-selling band in history The Beatles are considered by a number or journalists "the first" or "the original" boyband, "before anyone had thought of the term."  The Liverpool quartet known as The Beatles were not only the quintessential rock band, but many considered John Lennon, Paul McCartney, George Harrison and Ringo Star to be the original boy band -- especially in the early 1960s when young girls would scream at the top of their lungs and pass out upon first sight of the "Fab Four.  The Beatles inspired the decision to produce the 1966 television series The Monkees, which spawned the music group of the same name, formed by the four starring actors. The rock and pop band started a career in music after their songs from the TV series released as records resulted successful.
Question: How did the boy band evolve over the years?
Answer:
Barbershop quartets were popular into the earlier part of the 20th century.