I've been reading THE BRAVEST VOICES, an autobiography by Ida Cook. Ida and her sister, Louise, became opera lovers in their twenties and after a few years began to travel to hear their favorite operas. This began in the 1920s. They met many of the world's top singers and became close friends with many of them. The stories are quite incredible. In the late 1930s they became involved in getting Jews, and other who were severely at-risk, out of Germany. These stories are equally incredible. This must be the most heartwarming book I've ever read. Despite the horrors of the Nazis, the commitment of Ida and her sister, the courage, and the cleverness are just awesome.
It was originally published in 1950 as WE FOLLOWED OUR STARS, then in 2008 as SAFE PASSAGE, and lastly, THE BRAVEST VOICES in 2021. There was a film of it, but I haven't been able to find any information of it. Highly recommended.