The Ring of Ritornel (1968) - Charles Harness

The Ring of Ritornel is actually slightly less complicated than some of the other Harness stuff I've read. It involves a far future, human-led civilization, the Twelve Galaxies, which is just coming out of a long war with the planet Terror. (Which I readily guessed was a corruption of Terra: a pun later used by E. C. Tubb, I don't know if Harness was first to use it, though I wouldn't be surprised if it was used much earlier.) The new emperor is something of a despot, but is almost killed at the beginning of the action. Clones are made of him in case he dies, and his poet-laureate is killed and has his brain placed in a music-composing computer to try to save the emperor's life. The lead character is the laureate's brother, who is ignorant of his brother's fate, and who grows up to become a highly-placed legal representative for the Palace. He falls in love with the Emperor's "daughter", and as a result is sent to argue the Emperor's case that the planet Terror should be destroyed. But ... There's lots more going on: energy-eating insects, spiders, the competing religions of Alea and Ritornel, a superintelligent Pegasus Kentaur, beings of antimatter, the end of the universe ... Pretty fun, though at times the absurdities really went too far. It does have several of Harness's recurring tropes: cyclical universes, spiders, beloved brothers, lead characters who are lawyers ...

My personal favs are The Rose, The Catalyst, The Venetian Court.