According to the rubric accompanying his only song in troubadour manuscript C,[1] he was Mayestre Matieus de Caersi, that is, a Master of Arts from Quercy, possibly Cahors.
Matieu's lone surviving song is Tant suy marritz que no.m puese alegrar ("I am so afflicted that I cannot be happy"), a planh on the death of James I of Aragon (died 26 August 1276).
It is often compared and contrasted with another planh on James' death composed by Cerverí de Girona, Si per tristor, per dol no per cossir.
Structurally, Matieu imposes coblas capfinidas on what is otherwise the metric and rhyme form used by Raimbaut de Vaqueiras in Ara pot hom conoisser e proar.
Earlier Matieu had compared the sorrow of the people of James' lands as like that of the Britons bemoaning the loss of King Arthur: ben devetz aitant de dol aver cum per Artus agron silh de Bretanha.