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A suggestion for a theme to fit the loose threads, or in this case different songs without a common theme, is to use the title Looking For A Sign as a joiner. As a boy or girl goes through life, their parents are listening to sixties songs and each song is a reminder of an event such as thier parent getting a job or travelling or getting divorced. Then as the girl or boy growws up and has events occuring in their life the songs become more modern. You could have the same event occuring for parent and child with different songs for comparison. Even walking through the city looking for a toilet sign could bring on a cue for a sign. The set could be simple and use scene projection as you have a wide timeframe to show. Ever heard the song "Signs".
Regards Don