Source : Webster's Revised Unabridged Dictionary (1913)

Tone \Tone\, v. t. [imp. & p. p. {Toned}; p. pr. & vb. n.
   {Toning}.]
   1. To utter with an affected tone.

   2. To give tone, or a particular tone, to; to tune. See
      {Tune}, v. t.

   3. (Photog.) To bring, as a print, to a certain required
      shade of color, as by chemical treatment.

   {To tone down}.
      (a) To cause to give lower tone or sound; to give a lower
          tone to.
      (b) (Paint.) To modify, as color, by making it less
          brilliant or less crude; to modify, as a composition
          of color, by making it more harmonius.

                Its thousand hues toned down harmoniusly. --C.
                                                  Kingsley.
      (c) Fig.: To moderate or relax; to diminish or weaken the
          striking characteristics of; to soften.

                The best method for the purpose in hand was to
                employ some one of a character and position
                suited to get possession of their confidence,
                and then use it to tone down their religious
                strictures.                       --Palfrey.

   {To tone up}, to cause to give a higher tone or sound; to
      give a higher tone to; to make more intense; to heighten;
      to strengthen.