
"Say It Isn't So" was introduced by Rudy Valee in 1932. It was a smash hit that helped Berlin recover from losing his shirt in the stock market crash and suffering other personal troubles. Valee, the consummate crooner, said the song helped save his marriage, as "that song... it was all true, and all happening to me." It's a 32-bar tune with two 16-bar sections, the second one repeating the first 6 bars of the first one. Notice the standard turnaround at the end of the first section (G6, G#dim, Am7, D13) and the very often-used chord progression of the last 8 bars. In interval numbers, it’s 4, 4m, 3m, 6, 2, 5, 1. That's a standard ending to hundreds of 32 bar songs.