Final answer:
The hymn 'O Come All Ye Faithful' can be described with the musical words joyful, celebratory, and devotional, highlighting its happy spirit, festive mood, and worshipful nature during Christmas celebrations.
Step-by-step explanation:
Three musical words that describe the hymn O Come All Ye Faithful could be joyful, celebratory, and devotional. This hymn is a traditional Christmas carol that invites the faithful to come and behold the newborn King, Jesus. The word joyful captures the elated and happy spirit of the song, as it celebrates the birth of Christ. Celebratory reflects the festive mood the hymn encompasses, which is often sung during Christmas services and gatherings, marking it as a time of special observance and festivity. Lastly, devotional speaks to the religious and worshipful attitude the hymn conveys, as it is a call to worship and revere the divine moment of Christ's birth.