As the other Bachianas Brasileiras were written during the 1930s, the period of Gétulio Vargas' regime, No. 9 was the last one, written in the same year Vargas was deposed. Villa-Lobos had become associated with Vargas's government when it appointed Villa-Lobos music education superintendent for Rio de Janeiro.
Bachiana Brasileira No. 9 is the only one that does not have double titles (one title based on classical music forms and the other relating to Brazil in some manner). Instead, this eight-minute work (the shortest in the series) is in quintessentially Bachian form of the prelude and fugue.
The work is scored for string orchestra (Villa-Lobos also wrote a version of it for wordless choir, but this is rarely performed). The opening, marked with the Italian direction "vague and mystical" begins with a striking sonority using high strings. A very Bachian aria melody unfolds, with harmonization that is often bitonal.
The concluding fugue (this Bachiana being one of four in the series that end in a fugue) has a typical quick subject. It rises to a strong and calm conclusion that is a fitting end to one of the most famous series of classical compositions ever written in South America.