British journalist and photographer Alan Harper was still a student when he made his first trip to Chicago in 1979 in search of one of its most famous exports: the blues.
When he went back in 1982, he was armed with a camera and notebook. "It was a bit like a gap year that got out of hand," he says.
The Chicago blues in the late 1970s and early '80s was far from fashionable in the era of soul, funk and disco.
Additionally, the old blues neighbourhoods of the city's South and West Sides were blighted by neglect.
However, the few surviving original blues clubs had been joined by new establishments in mainly white neighbourhoods, and the city retained a lively blues scene where singers of the older, southern-born generation played alongside younger musicians.
One band, the Sons of Blues was so called because it featured Carey Bell's son Lurrie on guitar, and originally had Willie Dixon's son Freddie on bass.
Below, founding member Billy Branch blows his "harp" at Biddy Mulligan's, a club on 7644 North Sheridan Road.
Theresa Needham, 70, was the proprietor of the legendary Theresa's Tavern at 4801 South Indiana Avenue, which in 1982 was one of Chicago's few surviving original blues clubs.
She was born in Mississippi and arrived in Chicago in the early 1930s. She opened the club in 1949.
Although Theresa's has since closed down, a North Side club called B.L.U.E.S. has remained open since the late 1970s.
Guitarist and blues singer Johnny Littlejohn plays with bass player Harlan Terson at B.L.U.E.S.
Littlejohn played and sang in the traditional Mississippi style, and his artistic roots could be traced back through Elmore James to Robert Johnson and beyond.
Legendary blues impresario and radio DJ Big Bill Hill, and admirers, sit in his broadcast studio.
However by this time he wasn't broadcasting blues any more, but gospel music, and his studio served as his church.
He would also stand on the street outside and preach.
Singer-songwriter Willie Dixon performs at Stages, a theatre-sized music venue on North Clark Street.
Dixon arrived in Chicago from Mississippi in 1936, worked for Chess Records in the 1950s, and wrote a string of classics for renowned Chicago bluesmen including Muddy Waters and Howlin' Wolf.
Good Rockin' Charles gives a young French musician a harmonica lesson in the alley outside a club.
He was a fine musician who worked with some prominent bluesmen and recorded an album, but by 1982 he was rarely sober.
He died just seven years later, aged 56.
Singer and guitarist Buddy Guy is captured on stage at ChicagoFest 1979, an annual music festival organised by the mayor's office, which ran for five years on the city's dilapidated Navy Pier.
Guy was co-owner of a traditional blues club, the Checkerboard Lounge, on the city's South Side. But you were lucky if you saw him play there as he spent much of his time on tour.
At the Lounge, Walter Williams, known to all by his stage name of Lefty Dizz, is seen mid-solo.
An entertaining if unreliable character, he once missed a gig at his own birthday party.
More of Alan Harper's stories and pictures from his book, Waiting For Buddy Guy can be viewed on his website.