Oops, I actually meant Textures when I wrote “grains mode”.
In general, I think anything where there is an envelope per grain and you’re manipulating the size or shape of that envelope would sound quite different to what Textures does.
One idea was applying a filter and manipulating cutoff and/or resonance per grain, perhaps including having an envelope against each. I can imagine clouds (Clouds?) of notes billowing up as a lowpass opens up. Maybe long grains and each having its own ADSR and/or having the base cutoff for each jumping about.
Another idea was pitch. You could have a fairly subtle pitch spread per grain to create a kind of chorus. Or you could start with pitches jumping all over the show and reduce this modulation to shift into something more sonorous. Something a bit like the THX logo sound but via grains rather than sustained notes.
I also wondered about manipulating volume envelopes over time, e.g. going from very tight staccato blips to bigger clouds or from a backwards-feeling upwards saw shape to shorter attack and more release.
Anyway, I think I’ve given myself a bunch of ideas now.
I’m going to try my approach sending many midi notes (same pitch) to Sampler and modulating the playback start point. I’ve done this to make very basic sort of timestretch effects already.