Previous reviews have remarked on the lyrical prose which is indeed very lovely. The spiritual content has been compared to Hesse's Siddhartha which is a novel about the Buddha. Pederson does seem to draw on Buddhist themes.
A sculpture that is central to the narrative could be said to be an indirect reference to The Jewel in the Lotus which is a representation of the mantra Om mani padme hum as an image. The Wikipedia article I've linked discusses the significance of each word in the mantra. It relates to Buddhist enlightenment. Meditation, which is a means of achieving Buddhist enlightenment, is an important activity for the male and female protagonists in The Sapphire Song.
Metaxaeus, the sculptor, visualizes and sculpts a phoenix from a gemstone. The phoenix is conceptualized as the Western phoenix which rises from the ashes and therefore symbolizes reincarnation. This makes the Western idea of the phoenix compatible with Buddhism which also deals with reincarnation as the way in which karma is worked out. The working out of karma is definitely an important aspect of this story. Yet I think that Pederson also weaves the Chinese phoenix into his book through his plot. The Chinese phoenix is the fusion of yin and yang which represents the unity of male and female spiritual forces. (See The Legend of the Chinese Phoenix .) The arc of the narrative in The Sapphire Song is about the male and female protagonists dreaming about each other and seeking unification. This is why the Chinese phoenix is associated with weddings.
My research into the symbolism of Pederson's images helped me to appreciate The Sapphire Song more. I hope that this review will also be helpful to other readers who are seeking to interpret the spiritual journey of Pederson's characters.