His first two volumes of chansons are for four voices, and are settings of the Amours of Pierre de Ronsard, poems which describe the stages and incidents in a love affair gone sour.
Some of the harmonic language used in the chansons is daring, and approaches the experimental level of Vicentino; Bertrand uses microtones, including quarter-tones,[citation needed] as an expressive device in two of the pieces from the second book (1578).
The most extreme example of this is the last seventeen measures of the chanson Je suis tellement amoureux, in which Bertrand completely avoids diatonic writing, using "only chromatic and enharmonic, with no mixture of diatonicism except in an interval in the bassecontre and another in the hautecontre, made to express the word 'death'" (Reese 1954, 389) However, in a later edition of the same songs (published posthumously in 1587) his publisher removed the dots used as microtone accidentals; evidently they were either too hard to sing, or the notation was too unfamiliar.
Bertrand's sacred works, contained in his three publications of Airs spirituels and sonets chrestiens, are closely related stylistically to the contemporary psalm-settings by the Huguenots: they are simple both melodically and harmonically, and usually maintain a homophonic texture throughout.
Except for the origin of their tunes, they are very similar to some of the psalm settings by the Huguenot composer Claude Goudimel, who had been killed by Catholics in the St. Bartholomew's Day Massacre a decade earlier.