Backbones rhymes with:
cheekbones, cheekbones, crossbones, airfones, allophones, baritones, blackstone's, bridgestone's, businessphones, chaperones, cheekbones, cherrystones, cobblestones, cornerstones, crossbones, daimones, earphones, firestone's, flagstones, folkstone's, gallstones, gemstones, gladstones, gravestones, hailstones, halftones, headphones, headstones, homophones, hormones, keystone's, keystones, limestones, livingstone's, madstones, megaphones, microphones, milestones, moonstones, overtones, pheromones, redstone's, reflectone's, rhinestones, saxophones, silicones, telephone's, telephones, tombstones, undertones, waterstone's, wellstone's, yellowstone's
Backbones sounds like:
beekeeping, bisbing, bisping, bookkeeping