IPA: /ˈtoʊn.ləs.nəs/
KK: /ˈtoʊnˌlɛs.nəs/
The condition of lacking tone or pitch in voice or sound.
The singer's tonelessness made it difficult for the audience to enjoy the performance.
Tonelessness → It is formed from "tone" (from Latin "tonus", meaning sound or tone) and "-less" (meaning without) and "-ness" (meaning the state of). The word "tonelessness" refers to the state of being without tone or sound.
Think of being 'without' ('-less') a 'sound' ('tone') — that's what tonelessness means.