What this song does in a room
The first "alleluia" goes up and you can feel the ceiling lift. "Agnus Dei" is one of the few contemporary worship songs that functions as actual liturgy. When the room sings "holy, holy, are You Lord God Almighty," they are not singing a chorus, they are joining a chorus that has been going on without interruption since Isaiah saw the throne and the seraphim cried it out.
You can lead this song in a thousand-seat sanctuary or in a small chapel and it will fill the space available. It does that because the lyric is not asking anything of the room except to participate in what is already happening in heaven. The pressure is off. The room just steps into the song that is already being sung.
What this song is saying about God
The theology is concentrated. "Holy, holy" is the Trisagion, the ancient declaration of God's absolute otherness. "Almighty" is His unrivaled power. "Worthy is the Lamb" is the title bestowed on the slain and risen Christ in Revelation 5. The song moves between the throne of the Father and the throne of the Lamb, which is the Trinitarian core of Revelation's worship vision.
The pastoral move is gentle but powerful. The God who is holy and other is the same God who became the Lamb. The Lamb who was slain is the Lamb who is worthy. The distance and the nearness are held together in a single song. That is hard to do, and Smith does it without straining.
Scriptural backbone
Revelation 4:8: "And the four living creatures, each of them with six wings, are full of eyes all around and within, and day and night they never cease to say, 'Holy, holy, holy, is the Lord God Almighty, who was and is and is to come!'" The song's chorus is essentially this verse set to music. Pair it with Revelation 5:12: "Worthy is the Lamb who was slain, to receive power and wealth and wisdom and might and honor and glory and blessing!"
Isaiah 6:3 gives the throne-room precedent: "Holy, holy, holy is the LORD of hosts; the whole earth is full of his glory." And John 1:29 names the Lamb on earth: "Behold, the Lamb of God, who takes away the sin of the world." Reading any of these passages before the song, even briefly, hands the congregation the imagery they are about to sing. They will sing with their eyes more open.
How to use it in a service
This song is at home in Communion, on Easter, on Christ the King Sunday, in services centered on the cross and the resurrection. It also serves well as a doxology after a sermon on the holiness of God or the worthiness of Christ. It is not the song to use as a high-energy opener. It is a song that wants stillness around it.
Allow extended, unhurried repetition. The chorus is built for repetition because heaven's chorus never stops. Sing it four or five times if the room is with you. Strip it back at some point, perhaps to voices only or to voice and a single sustained chord, so the congregation hears their own voices clearly. That moment is often the most affecting one in the entire service.
This song pairs well with silence. Do not rush out of it into the next thing. Let the last chord ring, let the room breathe, then move.
Things to watch for as the worship leader
First, this song requires a leader who is willing to slow down. The tempo is 70 bpm, which is barely moving. If your instinct is to push energy, this is not the song to push. Trust the slowness. Resist the impulse to fill the gaps.
Second, the song is contemplative, but contemplative is not the same as boring. The dynamic arc still matters. Build through repetitions, strip back for the bridge or chorus, return for a final build. Without that arc, the song flattens and the congregation drifts.
Third, the melody sits high in the chorus. In Bb for men, the high "alleluia" can push for less-trained voices. In Eb for women, the climb is similar. If your room cannot reach the top comfortably, consider G for a mixed congregation, which lowers the chorus into a singable range for most.
Fourth, lyric familiarity matters. Some of your people learned this song in 1995. Some have never heard it. Pre-teach the chorus if the song is new, or open with a vocal-only repetition so the room can lock the melody. Do not assume.
A note for the team behind you (techs, vocalists, band)
For the band, the arrangement is sparse on purpose. Piano and pad should form the foundation. Acoustic guitar can layer in for harmonic warmth but should not strum percussively. Drums, if used, should enter late, with a soft kick and brushes or rods, never sticks. The song does not need a backbeat. It needs a pulse. Bass should sustain root notes rather than drive a line. Electric guitar should be ambient only, volume swells or sustained notes with reverb. No riffs.
For vocalists, the harmonies are the heart of this song. The "alleluia" section calls for a stacked vocal blend, ideally three or four parts. The harmonies should be sung pure, with minimal vibrato, so the chord rings cleanly. This is choral writing in a worship song's clothing. Lead vocal should sing the melody straight, with restraint. Save any improvisation for the very end, if at all, and even then keep it minimal.
For techs, the dynamic range on this song is wider than the volume range. The song should feel reverent throughout, never blasting. Reverb on vocals can be more generous than usual, almost cathedral-length, because the song's imagery is heavenly. Front of house should feature the vocal blend over individual voices. In-ear mix for the band should keep the piano and lead vocal central so phrasing stays locked. Have a plan for the quietest moment, often when the band drops out and voices carry alone. That moment lives or dies on monitor confidence. Coach the team that the silence between phrases is not a mistake. It is the song breathing.