undertone

acetone, allophone, altar stone, anglophone, anklebone, barbitone, baritone, bombardon, brain hormone, buffer zone, Canal Zone, cannon bone, cherrystone, cinder cone, cobblestone, coffin bone, collarbone, comfort zone, cornerstone, cortisone, crazy bone, crumple zone, curling stone, cuttlebone, demand loan, diaphone, Dictaphone, ecotone, epigone, fracture zone, francophone, frigid zone, frontal bone, funny bone, gramophone, growth hormone, hammerstone, herringbone, hold one's own, holystone, homophone, hydrophone, ice-cream cone, ironstone, kidney stone, knucklebone, leading tone, leave alone, let alone, lithopone, marrowbone, megaphone, mellophone, methadone, microphone, microtone, minestrone, monotone, neutral zone, on one's own, overblown, overgrown, overtone, plant hormone, polyphone, prednisone, provolone, quarter tone, rotenone, rottenstone, sacaton, saxophone, semitone, sex hormone, shacklebone, shatter cone, silicone, sousaphone, speakerphone, stand-alone, stepping-stone, telephone, temperate zone, temporal bone, thunderstone, Torreón, torrid zone, traffic cone, twilight zone, vibraphone, Yellowstone