The focus was on what evolutionary advantage music plays for humans and he mentioned six types of songs as roles for music. Those are friendship, joy, comfort, knowledge, religion, and love. He talked the most about knowledge songs and used an example of people knowing countries via the Animaniacs song set to the tune of "The Mexican Hat Dance." (Of course, I thought of Tom Lehrer's "The Elements" right away.) But he also put self-knowledge, including emotional growth into that category.
I was particularly interested in the story he told about his grandmother, a Holocaust survivor, who sang "G-d Bless America" every day and who learned how to play it on an electronic keyboard while in her 80's. I admit, however, that I'm not all that sure how this fits in with his hypothesis re: evolutionary advantage, though it does qualify as a song of joy.
I will wait a while before buying the new book, however, since evolution doesn't interest me nearly as much as other issues relating to musical cognition. The lecture did serve a hugely important purpose, however, since it got me to Levitin's website, where I discovered that the sites for each book include samples of the songs he references. Since he references such a wide range of material, nobody is likely to know all of it. (And I also don't necessarily know the title of a song, even if I know the song well. One of my pet peeves is that radio stations rarely tell you the title and singer nowadays, expecting you to go to their website for that info.)