What happens at a temple dedication?
Our modern temple dedications follow the pattern and agenda Joseph Smith set with the dedication of the Kirtland House of the Lord. At that dedication, the meeting proceeded like many church meetings, with prayers, hymns and sermons. President Smith then offered dedicated the temple by offering a prayer which he had recorded for that occasion (this prayer can be found in D&C 109). Following the prayer, they sang “The Spirit of God”. A few more remarks were given, including the prophet’s testimony and then they “sealed the proceedings of the day by a shouting hosa[n]nah to God and the Lamb 3 times sealing it each time with Amen, Amen, and Amen” (The Joseph Smith Papers. “Journal, 1835-1836“, p. 188). Four days later, another dedication service was held “for the ben[e]fit of those who could not get into the house on the preceding sabbath. … [T]he services of the day were commenced, prosecuted, and terminated in the same manner as at the former dedication and the spirit of God rested upon the congregation” (193).
Following this pattern, temple dedications may include a series of dedicatory sessions (although in more recent years dedications have been broadcast to nearby meetinghouses to accommodate more members who hold temple recommends). The dedicatory prayer is also written out and read, instead of the more free-form prayers we’re accustomed to. Those in attendance give the hosanna shout. Elder Lorenzo Snow described this ceremony:
“This is no ordinary order, but is—and we wish it to be distinctly understood—a sacred shout, and employed only on extraordinary occasions like the one now before us. We wish it also to be distinctly understood that we want the brethren and sisters not only to express the words, but that their hearts shall be full of thanksgiving to the God of heaven. …
“Now when we go before the Temple, and this shout goes forth, we want every man and every woman to shout these words to the very extent of their voices, so that every house in this city may tremble, the people in every portion of this city hear it, and it may reach to the eternal worlds.” (Teachings of the Presidents of the Church: Lorenzo Snow. “Chapter 10: Come into the Temples“).
Elder B.H. Roberts has shared his own testimony of these sacred and joyful moments:
“It is impossible to stand unmoved on such an occasion. It seems to fill the prairies or woodland, mountain wilderness or tabernacle, with mighty waves of sound; and the shout of men going into battle cannot be more stirring. It gives wonderful vent to religious emotions and is followed by a feeling of reverential awe—a sense of oneness of God” (Comprehensive History of the Church, vol. 3, p. 317).
And finally, in keeping with tradition, the choir and congregation sing “The Spirit of God”, with the choir singing the “Hosanna Anthem” written for the Salt Lake Temple dedication.
You can see an example of this pattern at the dedication of the Conference Center during the October 2000 General Conference. During the Sunday morning session, President Hinckley gave some remarks, instructed the congregation on the format of the hosanna shout, read the dedicatory prayer, and finally the choir and congregation joined in singing “The Spirit of God” with the “Hosanna Anthem”.