The Collaborative International Dictionary of English v.0.48:

Intonate \In"to*nate\, v. i. [L. intonatus, p. p. of intonare to
   thunder, resound.]
   To thunder. [Obs.] --Bailey.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Intonate \In"to*nate\, v. i. [imp. & p. p. Intonated; p. pr. &
   vb. n. Intonating.] [See Intone.]
   [1913 Webster]
   1. (Mus.) To sound the tones of the musical scale; to
      practice the sol-fa.
      [1913 Webster]

   2. To modulate the voice in a musical, sonorous, and measured
      manner, as in reading the liturgy; to intone.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Intonate \In"to*nate\, v. t.
   To utter in a musical or sonorous manner; to chant; as, to
   intonate the liturgy.
   [1913 Webster]

WordNet (r) 3.0 (2006):

intonate
    v 1: speak carefully, as with rising and falling pitch or in a
         particular tone; "please intonate with sadness" [syn:
         intonate, intone]
    2: recite with musical intonation; recite as a chant or a psalm;
       "The rabbi chanted a prayer" [syn: chant, intone,
       intonate, cantillate]

Moby Thesaurus II by Grady Ward, 1.0:

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