Swell
Swell scales each note's velocity, held from 1 to 127, for crescendos and fades. A Swell generator also has an Accent, which makes the beats louder still, up to 50%. Swell is one of the three shapes, each a percentage that ramps from a start to an end, which Generators describes: where each is set, which wins, and the settings they share. The Swell percentage runs from 0% to 200%.
Settings
The settings are those every shape shares, which Generators describes.
Applying the Generator
Set Swell in the + Swell section of a Scene page or a clip page, or make a Swell generator and add it to a chain, as swell: name, to paint one shape on many clips and change it in one place. examples/learning/16_bolero_swell.yml is one long crescendo.