The first reliable mention of Martini is found a document, dated 1473, declaring that "Giovanni d'Alemagna" had become a member of the Duke's chapel at Ferrara. He may have been born at Leuze or Tournai and have had brothers named Thomas and Petrus. The Duke Ercole I d'Este possibly announced his plans to hire Martini as early as 1471. Whatever the case, the partnership begun in 1473 was absolutely central to Martini's life and career. In 1474, the same year Dufay died, Martini briefly worked for Ercole's rival in Milan; except for this interlude, Martini was employed by the d'Estes until his death, during which time he was clearly a leading composer in Ferrara. The establishment's favor of him was expressed in his inflated salary, the benefices he received thanks to the Duke's help, and the house he was given. When Ippolito d'Este, then only eight years old, was installed as Archbishop of Esztergom, Hungary, Martini was part of the retinue that accompanied him there. Martini was clearly a well-respected and reasonably prolific composer. Eleven masses survive by him, as well as motets, psalms, hymns, magnificats, and numerous chansons. A huge, two-volume manuscript survives of sacred music by Martini and Giovanni Brebis, one of Martini's composer colleagues at the chapel in Ferrara. The music it contains is for double choir and is the earliest known music of the kind. A collection of chansons made for the marriage of Isabella d'Este to Francesco Gonzaga also prominently features Martini's work. His music is essentially conservative and reflects the influence of the previous generation, notably Dufay and Ockeghem, being more about formal/structural concerns than the musical expression of the text.