A proud fifteenth century Florentine organist produced one of the first documents of musical historiography. He collected the music of several generations of Italian composers into the lavish illuminated manuscript that would later be called the Squarcialupi Codex. He especially favored Florentines, but northern Italian musicians such as composer and theorist Jacopo da Bologna also feature prominently. Jacopo's music in the Codex shows a strong and creative musical intellect, as well as an individual who delighted in musical competitions with his contemporaries. Jacopo also seems to have been well-connected politically, as allusions to numerous Italian nobles and their affairs emerge from his compositions. Aquil' altera/ Creatura gentil/ Ucel de Dio (Proud eagle/ Noble creature/ Bird of God), though it contains no direct acrostic references, apparently honors such a noble patron. Two scintillating ceremonies have been suggested as occasions for its composition: the 1355 coronation of Emperor Charles IV in Milan, or the 1360 wedding between Gian Galeazzo Visconti, warrior count of Milan, and princess Isabella de Valois.
Whichever elevated ritual first heard the singing of Aquil' altera, the piece itself presented an outstanding and pathbreaking visage to the world. Aquil' altera follows the new secular form of the Italian trecento madrigal, a musical form that Jacopo and his generation (including Giovanni da Cascia and Magister Piero) themselves invented. The term madrigal may derive from carmen matricalis, merely indicating a song in the mother tongue of Italian. In the trecento, the madrigal became a standard form consisting of two sections contrasting in meter, and marked by extended opening melismas. Aquil' altera not only stretches the standard scoring from two voices to its three, but is one of only two surviving madrigals to give different texts to each of its three voices. All three texts refer in charged language to the noble eagle, and all three converge in the ritornello to suggest the eagle stands among us as a particular ruler (thus the political overtones involving men with eagles among their heraldic insignia). The madrigal pits two upper voices who enter sequentially and often imitate one another's virtuosic ornaments against a harmonic foundation in the bass voice. The ritornello relaxes from octuple meter into sextuple, and proceeds to converge musically as well as textually: the three voices conclude the fiery polyphony on a simple unison. The piece was popular enough to be reproduced in four of the time's most important secular collections, and later in an instrumental arrangement. ~ Timothy Dickey, Rovi