tremor - A slight shaking movement, such as one caused by an earthquake or instability; also a subtle or faint sign of emotion, such as fear or excitement in the voice or body.

Because he was nervous, his voice had a significant tremor during the presentation.
ringleader - Someone who is the main influence or motivator behind a particular action or event, especially a disruptive or controversial one.

The police managed to arrest the ringleader of the gang, who had coordinated the series of robberies across the city.