To find music that fits Of Mice and Men, one fun option would be to explore music from the 1930s, the time period when the book itself takes place. The Internet Archive, an open-source cultural repository, has some great playlists of early-twentieth-century music that would be a great start— ...
To find music that fits Of Mice and Men, one fun option would be to explore music from the 1930s, the time period when the book itself takes place. The Internet Archive, an open-source cultural repository, has some great playlists of early-twentieth-century music that would be a great start—here's one featuring music from the 1920s and 30s. Based on the titles, you may notice some familiar themes that reflect some of what you see in the book. Though the specific conflicts in Of Mice and Men are unique to George and Lennie, their life circumstances were very familiar to many who lived in that time period. Much of the music from that era reflects this struggle.
In your question, you specify that the songs should go with the book's important moments—what constitutes an important moment is probably up to an individual's discretion, and you'll have to decide which moments in the narrative speak most strongly to you. The good news is that many of the themes in Of Mice and Men are fairly universal, which means that they'll be easy to find represented in music from just about any era.
Here are a few examples you might consider that speak to significant elements of the narrative:
To reference the book's setting and its focus on the difficult lives of agricultural workers during the Great Depression, you might put Neil Young's "Harvest," Gillian Welch's "One More Dollar," or Bob Dylan's "Desolation Row."
Since George and Lennie spend a lot of time thinking about what life might be like someday, consider songs that focus on aspiration or hope—Sam Cooke's "A Change is Gonna Come" is one classic option, and Sharon Van Etten's "One Day" is great if you'd like something more contemporary. Since Steinbeck threads discussion of dreams through the narrative, you might also try Otis Redding's "I've Got Dreams to Remember" or Blondie's "Dreaming."
For the book's emotional climax—George's mercy killing of his best friend, Lennie—you might consider songs that deal specifically with feelings of regret, endings, or brotherhood. Fiona Apple's "Regret," St. Vincent's "Strange Mercy," Glen Hansard's "Brother's Keeper," and John Prine's "Summer's End" are all great options.