An obvious polymath, Saint-Georges was also an accomplished violinist at an early age (hence the comparison to Mozart) and became an accomplished composer in his own right as well. Saint-Georges was subsidized during his younger years by his father, but that money went to his apparently white and legitimate half-sister when his father died, leaving Saint-Georges to support himself by what he earned from his music and from the Orchestras he conducted. He continued to enjoy both tremendous popularity, but also periodic racism against him. He became a great favorite of Marie Antoinette. Saint-Georges began writing operas, met other famous talents in the music world, including the actual Mozart and Haydn. During this time his mother, who had continued to live with him, died - apparently still at least technically a slave by legal status if not in how she lived.
Subsequently, Saint-Georges spent time in England, including rubbing elbows with the Prince of Wales. Throughout his life among the nobility and wealthy, Saint Georges was an ardent supporter of the abolition of slavery.
When the French Revolution began, Saint-Georges volunteered, and headed up a legion of 'colored' troops, holding the rank of colonel. He fought on the side of the Republic against the monarchists, was imprisoned during the 'Terror', was released when the worst excesses of the Revolution were over. Without the patronage afforded him by the nobility prior to the revolution, he was somewhat less successful.
At one point he left France for about two years when there was a slave revolt on Caribbean island where he was born. Two years later he returned to France, again tried to rejoin his legion and again began composing and conducting music, as well as resuming playing the violin. He died in 1799 in comparative poverty. He left behind as his legacy a large body of musical compositions, including operas, symphonies, concertos, chamber music, music for string quartets, and vocal music, many of which are still performed and recorded.
And he was also a character in the TV Show Nicholas Le Floch (Le Dîner de Gueux)!