The Collaborative International Dictionary of English v.0.48:

Dulcet \Dul"cet\, a. [OF. doucet, dim. of dous sweet, F. doux,
   L. dulcis; akin to Gr. ? . Cf. Doucet.]
   1. Sweet to the taste; luscious. [Obs.]
      [1913 Webster]

            She tempers dulcet creams.            --Milton.
      [1913 Webster]

   2. Sweet to the ear; melodious; harmonious.
      [1913 Webster]

            Their dainty lays and dulcet melody.  --Spenser.
      [1913 Webster]

WordNet (r) 3.0 (2006):

dulcet
    adj 1: extremely pleasant in a gentle way; "the most dulcet
           swimming on the most beautiful and remote beaches"
    2: pleasing to the ear; "the dulcet tones of the cello" [syn:
       dulcet, honeyed, mellifluous, mellisonant, sweet]

Moby Thesaurus II by Grady Ward, 1.0:

80 Moby Thesaurus words for "dulcet":
   achingly sweet, affable, agreeable, agreeable-sounding, amiable,
   amicable, appealing, ariose, arioso, blissful, canorous, cantabile,
   catchy, cheerful, compatible, complaisant, congenial, cordial,
   desirable, en rapport, engaging, enjoyable, euphonic, euphonious,
   euphonous, fair, fair and pleasant, felicific, felicitous, fine,
   fine-toned, genial, golden, golden-tongued, golden-voiced, good,
   goodly, gracious, grateful, gratifying, harmonious, heart-warming,
   honeyed, likable, melic, mellifluent, mellifluous, mellisonant,
   mellow, melodic, melodious, music-flowing, music-like, musical,
   nice, pleasant, pleasant-sounding, pleasing, pleasurable,
   pleasure-giving, pleasureful, rewarding, rich, satisfying,
   silver-toned, silver-tongued, silver-voiced, silvery, singable,
   songful, songlike, sonorous, sweet, sweet-flowing, sweet-sounding,
   tunable, tuneful, welcome, winning, winsome