A call for volunteers is raised. The crowd murmurs and shuffles uncertainly, there are a lot of sideways glances, but no-one moves forward. After a tense few seconds, however, one person raises their hand. Cue a musical crescendo as more people join in - and ultimately everyone has volunteered... or, at least everyone important to the story. This is a sister trope of Slow Clap. Perhaps both could be fit under a "One Starts The Trend" umbrella, encompassing applause, volunteering, singing (in silence one person starts to sing and everyone joins in), cheering, etc..? Suggestions welcome.
Hello, Unknown Troper. You'll need to get known to lend a hand here.