This component spawns Audio Source components along the river spline.

Such a component can be created through:

GameObject->Audio->River Audio Zone

In the screenshot above, spawning is restricted to slope angles between 15º and 90º to filter out sections that likely represent a cascade. This is a straightforward yet powerful way to position specific audio clips.

The component also linearly attenuates the volume of the created Audio Zones, based on the camera’s distance to them. Something Audo Emitters themselves don’t handle well enough.