Who was the first musician to make a career solely from composing music?

The first musician to make a career solely from composing music is considered to be Guillaume Dufay (1397–1474). Dufay was a Franco-Flemish composer, singer, theorist, and diplomat of the early Renaissance. He was among the most famous composers of his time and is often regarded as one of the most influential figures in the history of Western music.

Dufay was born in Hainaut, in what is now Belgium, and spent most of his career in Italy, where he served as a singer and composer at the papal chapel in Rome and at the court of the Este family in Ferrara. He also traveled extensively throughout Europe, visiting France, England, and the Netherlands.

Dufay's music is characterized by its use of rich polyphony, complex rhythms, and expressive melodies. He composed a wide variety of vocal and instrumental works, including masses, motets, secular songs, and instrumental pieces. His music was highly influential and helped to shape the development of Western music in the 15th century.

Dufay was also an important music theorist and wrote several treatises on music. He was the first composer to use the term "musica reservata" to describe a new style of polyphonic music that was more complex and sophisticated than the traditional polyphony of the time.

Dufay's music continues to be performed and enjoyed today, and he is considered one of the most important figures in the history of Western music.