During the first decade of the 17th century he probably traveled widely in Italy, meeting composers, acquiring patrons at various aristocratic courts, and absorbing the musical styles at each locale.
This was a time of transition in music history, as the polyphonic style of the late Renaissance was giving way to the widely diverse practices of the early Baroque, and d'India seems to have acquired an unusually broad grasp of the total stylistic practice in Italy: the expressive madrigal style of Marenzio, the grand polychoral work of the Venetian School, the conservative polyphonic tradition of the Roman School, the attempts to recover the music of the ancient world in monody and its larger vehicle, the newly developing opera, as well as the mannered, emotionally intense chromatic style of Carlo Gesualdo in Naples.
[1] d'India's output consisted of music in most of the vocal forms of the time, including monodies, madrigals, and motets.
His monodies, the most numerous and significant portion of his work, were of many types: arias, both through-composed and strophic, variations over ground basses, laments, madrigals in the monodic style, and others.
Some of d'India's later music is unusual in showing aspects of the influence of almost all of the contemporary composers in Italy within a single piece.