Overtone rhymes with:
undertone, acetone, baritone, blackstone, bloodstone, bluestone, blystone, bridgestone, brookstone, brownstone, capstone, cherrystone, cobblestone, cornerstone, coverstone, curbstone, dialtone, executone, eyestone, featherstone, finestone, firestone, flagstone, folkstone, freestone, gallstone, gemstone, gladstone, goldstone, gravestone, greenstone, greystone, grindstone, hailstone, halftone, headstone, instone, johnstone, keystone, levinstone, lightstone, limestone, livingstone, lodestone, medstone, milestone, millstone, monotone, moonstone, nutone, pepitone, pipitone, poundstone, redstone, reflectone, rhinestone, richstone, sandstone, silverstone, steppingstone, tombstone, touchstone, undertone, waterstone, weatherstone, wedgestone, whetstone, whitestone, yellowstone
Overtone sounds like:
operation, opportune, overdone, overridden, overtime, overton, overwritten