I'm confused about GPO's trills. I see "playable" trills which use keyswitches and "auto" trills that use MIDI controls. From the name I assume playable trills are not sampled trills, but are GPO alternately playing two sampled non-trilled notes (although I'd call that "played" rather than "playable" so I've probably got it wrong). What is "auto trill"?

I use GPO4 as a plugin in Sibelius 6 and know that Sibelius does not use GPO's playable trills. I also know that for instruments with slow attack Sibelius's trills are very weak. Would I be better off putting in a KS sequence and using GPO's playable trill? Does the playable trill support compensate for slow attack?