“While awaiting the release of ”California Dreamin’,’ band member Denny Doherty was prodding songwriter John Phillips to come up with some new material,” (Songfacts). “Phillips said he would come back in the morning with ‘a song with universal appeal.’ Ignoring the sarcastic comments from the group members, Phillips came up with ‘Monday, Monday’ (1966). It’s about the lousy feeling that comes with the end of the weekend and beginning of another workweek.
This was the first Hot 100 chart-topper with a day in the week in the title, and the only one with ‘Monday.’ (‘Manic Monday’ by the Bangles and “Rainy Days And Mondays” by the Carpenters both stalled at #2.) … Denny Doherty, who sang lead on this song, thought very little of ‘Monday Monday’ when they recorded it. ‘Nobody likes Monday, so I thought it was just a song about the working man,’ he said. ‘Nothing about it stood out to me; it was a dumb f–kin’ song about a day of the week.’ As you can imagine, he was taken by surprise when the song became a huge hit. Doherty wasn’t alone in his incredulity: Mama Cass and Michelle Phillips didn’t like the song either, and John Phillips claimed he had no idea what the song meant.”
Starting in F# major, the tune features some brief harmonic sidesteps along the way, but doesn’t modulate in earnest until 1:41, when it shifts up to G# major.