The Collaborative International Dictionary of English v.0.48:

Soften \Sof"ten\, v. t. [imp. & p. p. Softened; p. pr. & vb.
   n. Softening.]
   To make soft or more soft. Specifically:
   [1913 Webster]
   (a) To render less hard; -- said of matter.
       [1913 Webster]

             Their arrow's point they soften in the flame.
                                                  --Gay.
       [1913 Webster]
   (b) To mollify; to make less fierce or intractable.
       [1913 Webster]

             Diffidence conciliates the proud, and softens the
             severe.                              --Rambler.
       [1913 Webster]
   (c) To palliate; to represent as less enormous; as, to soften
       a fault.
       [1913 Webster]
   (d) To compose; to mitigate; to assuage.
       [1913 Webster]

             Music can soften pain to ease.       --Pope.
       [1913 Webster]
   (e) To make calm and placid.
       [1913 Webster]

             All that cheers or softens life.     --Pope.
       [1913 Webster]
   (f) To make less harsh, less rude, less offensive, or less
       violent, or to render of an opposite quality.
       [1913 Webster]

             He bore his great commision in his look,
             But tempered awe, and softened all he spoke.
                                                  --Dryden.
       [1913 Webster]
   (g) To make less glaring; to tone down; as, to soften the
       coloring of a picture.
       [1913 Webster]
   (h) To make tender; to make effeminate; to enervate; as,
       troops softened by luxury.
       [1913 Webster]
   (i) To make less harsh or grating, or of a quality the
       opposite; as, to soften the voice.
       [1913 Webster]

WordNet (r) 3.0 (2006):

softened
    adj 1: toned down
    2: being or made softer or less loud or clear; "the dull boom of
       distant breaking waves"; "muffled drums"; "the muffled noises
       of the street"; "muted trumpets" [syn: dull, muffled,
       muted, softened]