Overtones rhymes with:
undertones, baritones, blackstone's, bridgestone's, cherrystones, cobblestones, cornerstones, firestone's, flagstones, folkstone's, gallstones, gemstones, gladstones, gravestones, hailstones, halftones, headstones, keystone's, keystones, limestones, livingstone's, madstones, milestones, moonstones, redstone's, reflectone's, rhinestones, tombstones, undertones, waterstone's, yellowstone's
Overtones sounds like:
operating, operation's, operations, operations', overdoing, overeating, overheating, overrating, overriding, overwriting