However, the forces destined to end the hold of the Classical style gathered strength in the works of many of the above composers, particularly Beethoven. The most commonly cited one is harmonic innovation. Also important is the increasing focus on having a continuous and rhythmically uniform accompanying figuration: Beethoven's Moonlight Sonata was the model for hundreds of later pieces—where the shifting movement of a rhythmic figure provides much of the drama and interest of the work, while a melody drifts above it. Greater knowledge of works, greater instrumental expertise, increasing variety of instruments, the growth of concert societies, and the unstoppable domination of the increasingly more powerful piano (which was given a bolder, louder tone by technological developments such as the use of steel strings, heavy cast-iron frames and sympathetically vibrating strings) all created a huge audience for sophisticated music. All of these trends contributed to the shift to the "Romantic" style.