The Collaborative International Dictionary of English v.0.48:

Psalmody \Psal"mo*dy\, n. [Gr. ?; ? psalm + ? a song, an ode:
   cf. F. psalmodie, LL. psalmodia. See Psalm, and Ode.]
   The act, practice, or art of singing psalms or sacred songs;
   also, psalms collectively, or a collection of psalms.
   [1913 Webster]

WordNet (r) 3.0 (2006):

psalmody
    n 1: the act of singing psalms or hymns [syn: psalmody,
         hymnody]