The 16th-century organ of the cathedral is the pride of the Valvasone community and is certainly one of the most interesting art pieces in the entire Friuli, both for its musical value and for the importance of the pictorial decorations that adorn it.

In fact, it is a unique instrument of its kind, commissioned in 1532 to the great organ master Vincenzo de Columbis (Casale Monferrato, circa 1490 – Venice, 1574), with the contribution of the greatest Friulian painter of the time, Giovanni Antonio de’ Sacchis, known as "il Pordenone" (circa 1484 – 1539).

The work began in 1533 with the necessary architectural works to position the organ on a choir loft anchored to the right wall, and in the same year, the instrument came into operation, although the construction of the case that covers it was not completed before 1535.

At that point, the decorative endeavor began, which engaged until 1538 the carver Girolamo di Venezia and the gilder Tommaso Mioni from Udine, who proposed an elegant repertoire, made of masks and scrolls, now of Mannerist taste.

For the doors, however, "Pordenone" was contacted, who in 1537 received an advance of 55 ducats for the realization of the panels on Eucharistic themes; unfortunately, two years later, the painter died in Ferrara, leaving the realization just begun incomplete.

The effort made for this instrument, hiring the most esteemed organ builders, craftsmen, and artists of the time and facing such significant expenses, is an eloquent indicator of the attention paid in Valvasone in the 16th century to musical activity, promoted by two centers, both closely linked to the lords of Valvason: the castle and the parish church.

In the latter, the liturgical-musical activity must have been very intense, as numerous documents testify, which, among other things, tell of the frequent performance of sacred representations, such as that of Feo Belcari's "Abraam e Isac," linked to Eucharistic themes and therefore very suitable for the environment given the presence of the precious linen.

"Il Pordenone" was one of the most renowned painters of the time and was considered one of the greatest interpreters of Renaissance art, for the monumentality he knew how to confer to figures, often using daring and astonishing perspective foreshortenings, and inserting them into compositions of new invention. The artist had already demonstrated his creativity in the ornamentation of organs, working both for the cathedral of Spilimbergo (in 1523-1524) and for that of Udine (in 1527-1528). "Pordenone" died in 1539, probably leaving only the sketch of the scenes present on the panels. The painter Pomponio Amalteo from San Vito (Motta di Livenza 1505 – San Vito al Tagliamento 1590), a student and son-in-law of de Sacchis, was called to complete the work in 1549.

This is not the only episode of its kind, as Pomponio also "inherited" other commissions left unfinished by his father-in-law, completing them with the same language as his master, albeit through a stylistic approach of lesser quality.

Although the iconographic program of the pictorial decoration of the instrument is not precisely known – nor who was its inspirer – the reference to the Body of Christ (which gives the church its title) is always central, and the connection with the cult of the sacred relic is evident; however, according to some interpretations, in the Valvasone paintings, there would be a subtle polemic against the Roman church and an attention in favor of the Lutheran movement (the same possibility is suggested for the paintings of the Spilimbergo organ), which seems to have enjoyed some sympathy among some members of the Valvasone family, as well as in other noble Friulian families of the time.

However, on the panels, whose design is attributed to "Pordenone," Old Testament themes are depicted: when closed, they present the grand scene of the Fall – with some central figures autographed by the great master – a biblical episode that represents an evident prefiguration of the Eucharist, while when open, as they are when the instrument is in operation, on the left is placed the Sacrifice of Abraham and on the opposite side the Sacrifice of Melchizedek, also events commented on by tradition as Eucharistic symbols, executed by Amalteo in 1549 following the design of his father-in-law.

Instead, on the balcony appear panels, entirely conceived and realized by Pomponio Amalteo at the beginning of the '50s, with episodes taken from the Gospels: from the left, the Wedding at Cana, the Expulsion of the Merchants from the Temple, the Pool of Bethesda, the Multiplication of the Loaves, and the Conversion of Mary Magdalene. All events are linked in various ways to an exegesis of Eucharistic nature, as prefigurations in other forms of the Sacrament.

Pomponio is also responsible for the frescoed friezes with grotesque motifs on the sides of the instrument.