in Ardour what is the correct way to do a “ritardando” in an audio file?
Using “New tempo”, “Edit Tempo”, “ramped” has no effect, but maybe it’s reserved for MIDI.
In an audio track how do you do it?
Ardour does not offer this at this time.
There are some “tape effect” plugins which can do something similar, and can be automated.
In Ardour plugin selector, searching for “tape”, I can’t find the right tape effect plugin that does this gradual increase or decrease in tempo (without changing the pitch, this is important). Some advice?
Ardour does not provide very many plugins itself, and certainly not one that does this. You’d need to find a 3rd party one for the platform you are using.