This arrangement of O Holy Night is perfect for youth choirs or young women's ensembles.  The accompaniment supports the voice parts, which are unison for the first half of each of the 2 verses.  The final 8 measures include an optional third harmony vocal at the climax.  The accompaniment includes cue notes for organ pedal.  Voice range is from Bb below Middle C to high F.  Read more in the blog post, O Holy Night for Youth Choir.