The DDLY Dynamic Delay from iZotope is a plug-in featuring two delay lines that respond dynamically to the source material. You can adjust the threshold to split the signal based on transients, and then send the signal down two separate analog or granular delay paths. For instance, one could set up the delay on a drum track to only add echo to the harder attacks of the kick and snare, without adding delay to the buzz from the snares, room noise, or a sloppy high hat that would make the mix sound muddy or crowded.
It is easy to emphasize the full range of the vocal take with a subtle delay on the verse and a more intense delay on the bigger moments in the chorus. Try it on guitars to add delay and echo to only the loudest parts of a performance, without touching the more intimate moments. In all these scenarios, the delay can be automated over the course of a whole mix to add movement and variety.
DDLY is compatible with Mac and Windows operating systems. It will work in AU, VST2, VST3, RTAS, and AAX formats.