"The Singing Stones" is a 1968 novel by Juanita Coulson, published as an Ace Double, along with Derai by EC Tubb. At the time of publishing, Coulson had published only one other book, but was already well known in the science-fiction community for her work on the fanzine Yanro, together with her husband, Robert Coulson. She would write many other books, mostly in the 1980s.
All of which I din't know as I begin to read the book. Geoff Latimer is an officer in the Terran Federation's Ethnic Protection Division. This means he is a bureaucrat tasked with making sure that human rights are respected on worlds that are part of, or allied, with the Federation. But the Federation's bureaucracy means that lower-technology civilizations should be allowed to develop at their own pace. On Deliyas, the planet where he is posted, the medium-technology civilization exploits the low-technology system of the moon of Pa-Liina, using its people as "indentured servants", using the letter of the law to enslave another people. Geoff is unhappy with Deliyas, but can do nothing about it until odd stones, the singing stones of the title, appear. Seemingly ordinary opals, contact with them gives people a strong hallucination of hearing psychic music, and which also seems to cause permanent physical and psychological changes to the listener. Are the Singing Stones the key to the liberation of the Pa-Liinans, or are they an insidious trap?
What was of interest to me about this book was the sophisticated and political backstory, where the question of promoting human rights was contrasted with the idea of allowing civilizations to evolve their own institutions...next to the action part of the book, which involved swords, laser beams, gryphons and crossbows. In what has been a surprisingly frequent direction in Ace Doubles, our science-fiction story turns into feudal warriors fighting with feudal weapons in a weird mixture of fantasy and science-fiction.
Another interesting thing for me was the year. 1968, I said, but when I wrote those numbers out, I was thinking of my science-fiction timeline. But, obviously, that timeline also coincided with the real world timeline. The presence of stones that can magically make people hear music in their heads is obviously inspired by the use of psychedelics in the 1960s. The political situation, where feudal natives fight against an imperial power, is not exactly some type of parallel to The Vietnam War, but reading this book, it is impossible to forget that it was written with The Vietnam War in the background. While it is possible to read this book as "just" an adventure story, it is hard to miss it as a very topical piece of work, as well.