While the harpsichord looks like a piano, its internal mechanism is entirely different. In a piano, hammers strike the strings; in a harpsichord, the strings are plucked by small plectra (traditionally made of crow quills). Because the strings are plucked with a uniform force, the player cannot change the volume by pressing the keys harder or softer. This lack of dynamic control is why many harpsichords have two keyboards (manuals)—one set to a louder volume and one to a softer volume. It was the dominant keyboard instrument of the Baroque era, defining the sound of composers like Vivaldi and Bach. The 'twanging' sound of the harpsichord is rich in high harmonics, which helped it cut through the sound of string ensembles in small chambers.