Perhaps the best-known piece of music by Guillaume Dufay—Nuper rosarum flores—was written for the dedication of a church. His stunning four-voiced motet graced the festivities in 1436 when the Pope himself consecrated the new cathedral Santa Maria del Fiore in Florence. Dufay's three-voiced hymn setting, Urbs beata Ierusalem, also serves the liturgy for church dedications; it is undeservedly much more obscure. Massive churches and cathedrals dominated the late medieval and early modern cityscape, and involved years—even decades—of civic labor, as well as staggering public cost. The consecration of a new church was an event worthy of rejoicing, a milestone in the life of a city and in its public relationship to God. A splendid and solemn liturgy celebrated that dedication, and the day became an annual feast in the city thereafter. When Dufay set Urbs beata Ierusalem, the Vespers hymn for all church dedications and their anniversaries, he was treading on holy ground.

The plainchant hymn Urbs beata Ierusalem, both musically and textually, adopts a tone fitting for its lofty occasion. The six stanzas of text brim with powerful scriptural echoes: the miraculous and holy dedication of the first Temple of Jerusalem by King Solomon, the theology of St. Peter (the "rock" himself) of Christ as the cornerstone for the building of His living church, and the vision of St. John after the Apocalypse of the heavenly city, New Jerusalem, where God and His people live eternally. The chant melody, as well, reflects the solemnity of its occasion in music. Its anonymous composer crafted a series of six short phrases, every second progressing to a strong cadence. The very opening phrase includes a striking B flat, yet proceeds to a rough-hewn downward leap to D. Throughout, the flinty melody balances a wide range and some difficult leaps with steady progress to each cadence.

Dufay matches this solemnity in his setting. He retains the chant melody in the top voice, with its strongly defined cadential goals and its wide range (the accompaniment even ventures above the melody once). Dufay follows the early chromatic coloration of the chant, and similarly inserts several poignant B flats in the melody and tenor voices. He supports this melody with a rather archaic-sounding harmonic structure, filled with hints of fauxbourdon, awkward progressions, and chords of open fifths. The final phrase he strengthens with a broad rhythmic extension of the melody, and some rhythmic near-imitation among all three voices.

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