Bel canto singing was a virtuosic skill not only for sopranos, but for altos, tenors, and baritones. The singer was expected to have flawless technique, a great purity and brilliance of sound, and a mastery of embellishments and improvisation. Because of the high demands and required skills, the singers became the stars of the show and even out-shined the composers. The singers gained such egos, they'd often rewrite the composers music and fight over parts. Often the sopranos would count the number of measures in their arias, if one's was longer than the other's, the soprano with the shorter aria would demand that more be written for her. In some cases, a singer would embellish and rewrite the music beyond the composer's recognition!
Several of these operas are still performed today with the most popular being Rossini's Il barbiere di Siviglia, Donizetti's Lucia di Lammermoor, and Bellini's Norma. Though the bel canto operas fell out of favor after the likes of Verdi, Wagner, and Meyerbeer, they were revived in the mid 20th century as singers like Maria Callas and Dame Joan Sutherland brought the spotlight back to them.
