The Collaborative International Dictionary of English v.0.48:

Solmization \Sol`mi*za"tion\, n. [F. solmisation, fr. solmiser
   to sol-fa; -- called from the musical notes sol, mi. See
   Sol-fa.] (Mus.)
   The act of sol-faing. [Written also solmisation.]
   [1913 Webster]

   Note: This art was practiced by the Greeks; but six of the
         seven syllables now in use are generally attributed to
         Guido d' Arezzo, an Italian monk of the eleventh
         century, who is said to have taken them from the first
         syllables of the first six lines of the following
         stanza of a monkish hymn to St. John the Baptist.
         [1913 Webster]

               Ut queant laxis
               Resonare fibris
               Mira gestorum
               Famuli tuorum
               Solve polluti
               Labii reatum,
               Sancte Joannes.
         [1913 Webster] Professor Skeat says the name of the
         seventh note, si, was also formed by him [Guido] from
         the initials of the two words of the last line; but
         this is disputed, Littr['e] attributing the first use
         of it to Anselm of Flanders long afterwards. The
         syllable do is often substituted for ut.
         [1913 Webster]

WordNet (r) 3.0 (2006):

solmisation
    n 1: a system of naming the notes of a musical scale by
         syllables instead of letters [syn: solmization,
         solmisation]