The Collaborative International Dictionary of English v.0.48:

Intone \In*tone"\, v. t. [imp. & p. p. Intoned; p. pr. & vb.
   n. Intoning.] [LL. intonare, intonatum; pref. in- in + L.
   tonus tone. See Tone and cf. Entune, Intonate.]
   1. To utter with a musical or prolonged note or tone; to
      chant; as, to intone the church service.
      [1913 Webster]

   2. To speak with a distinctive or unusual tone in the voice,
      or in a monotone; as, the professor intoned his lectures
      as though by rote.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Intone \In*tone"\, v. i.
   To utter a prolonged tone or a deep, protracted sound; to
   speak or recite in a measured, sonorous manner; to intonate.
   --Pope.
   [1913 Webster]

WordNet (r) 3.0 (2006):

intone
    v 1: utter monotonously and repetitively and rhythmically; "The
         students chanted the same slogan over and over again" [syn:
         tone, chant, intone]
    2: recite with musical intonation; recite as a chant or a psalm;
       "The rabbi chanted a prayer" [syn: chant, intone,
       intonate, cantillate]
    3: speak carefully, as with rising and falling pitch or in a
       particular tone; "please intonate with sadness" [syn:
       intonate, intone]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "intone":
   anthem, ballad, carol, chant, chirp, chirrup, choir, chorus, croon,
   descant, do-re-mi, hum, hymn, intonate, lilt, minstrel, pipe,
   psalm, quaver, roulade, serenade, shake, sing, sing in chorus,
   sol-fa, solmizate, tremolo, trill, troll, tweedle, tweedledee,
   twit, twitter, vocalize, warble, whistle, yodel