Why did singers object to the orchestration in Gioachino Rossini’s La cambiale di matrimonio?

Singers were indignant regarding the orchestration in Gioachino Rossini’s first opera buffa, La cambiale di matrimonio (1810), because it was considered unusual.1

At this early stage in his career, Rossini was beginning to break away from traditional operatic conventions. He eventually moved toward a style that restored the orchestra to a more prominent role, effectively placing the singer at the service of the music rather than the other way around.1