The 1900s : the birth of the recording industry -- The 1910s : stage, sheet music, and disc : a new synergy -- The 1920s : the jazz age -- The 1930s : brother, can you spare a dime? -- The 1940s : war at home, war abroad -- The 1950s : all shook up -- The 1960s : the rock invasion -- The 1970s : the balkanization of popular music -- The 1980s : the rise of the music video star -- The 1990s : the digital revolution begins.