Brunel enjoyed an exceptionally high reputation during his lifetime. Numerous writers, including Cosimo Bartoli, Cinciarino, Jacopo Corfini and Luigi Dentice, praised his skills. Bartoli wrote that Brunel played "with more grace, with more art and more musically than any other, whoever he may be." However, few of his works survive.
The most important pieces, a number of ricercars from the so-called Bourdeney Codex, were attributed to Brunel by Anthony Newcomb in 1987. These works are of considerable importance in the evolution of the genre: there are frequent instances of advanced contrapuntal techniques such as inversion and augmentation, hexachord transpositions (inganno) of the subjects. Some of the pieces even employ countersubjects.
Two ricercares also appear in another mansucript: one imitative, structured like a motet, and the other completely devoid of any imitative passages.
One other piece was attributed to Brunel by Knud Jeppesen: an organ mass discovered in the 1940s in manuscripts that were kept in the main church of Castell'Arquato. The mass, subtitled Messa de la dominica, is signed Jaches at the end of the last Kyrie verset. It is a typical Italian organ mass, consisting of many short pieces for the alternation practice.
All of the pieces are in four voices, but the texture is frequently interrupted either by passages in three voices, or with chordal passages which include chords of five, six, or even seven notes.
