simple past tense and past participle of tone
"The singer's voice sounded deep and resonant after she had toned it down from her usual high notes."
having or characterized or distinguished by tone or a specific tone; often used in combination
"full-toned"
"shrill-toned"
"deep-toned"
Having a (specified kind of) tone.
"The director asked the actor to tone down his voice for the quiet scene."