The Collaborative International Dictionary of English v.0.48:

Choral \Cho"ral\, a. [LL. choralis, fr. L. chorus. See
   Chorus.]
   Of or pertaining to a choir or chorus; singing, sung, or
   adapted to be sung, in chorus or harmony.
   [1913 Webster]

   Choral service, a service of song.
      [1913 Webster] Choral