the technique of using a flex machine to record incoming audio and then immediately play it back is exactly a technique i have been using. you can use it to immediately process, pitch shift, or slow down the audio. however, you have to be a little careful, as the playback can’t get ahead of the recording, otherwise you run into issues. this was mention by someone above as well. it’s nice too, because you can create some background from the incoming audio as well, that nicely evolves if you creatively use playback trigs.
i hate to spam this post, but i describe in pretty good detail my setup and include an example result of this technique here: The Octatrack can be quite granular-esque [example inside]