Hi! I'm using Notion3, a wonderful piece of software for composition and notation, and I recently bought GPO4.
I'm very glad I got GPO. It's a great deal: sounds are great, samples are dry and clean, controls are modern and efficient, and it's very consistent in sounds organization. Notion3 is completely integrated with the library, with presets and custom rules.
The only problem I haven't been able to figure out: how to play a trill or a tremolo from a note in the score, in solo strings and in timpani. Not even in Custom Rules is possible to have them playing.
I know the samples on these particular instruments are meant to be played in a performance, meaning that the user has to manually 'roll' the timpani or the tremolo repeating a note at the desired speed. But, shouldn't there be an option so the trill or tremolo plays automatically from the written note? I think GPO4 is great for performance, everything is mapped to notes and keyswitches so anyone proficient with a keyboard can become a timpanist, a violinist.. but what if you need GPO to write arrangements or just write music?
I see there are 2 sets of instruments; the 'standard' presets and the 'notation' presets. I think the notation sounds, not intended for performance, should play looped trills and tremolos just from the elements and markings in the score and not demand a player to repeat a note manually.
As a result, I don't have any solo string trills, tremolos, or timpani rolls available for my composing work. I have to use other libraries for these instruments, specially the timpani. It's the only thing that dissappointed me about GPO4 - so much, that I still believe I haven't tried everything yet and that there's a solution somewhere, like editing the sound files or something.
Re: GPO4, Notion3, solo string tremolos and trills.
It sounds like you understand the situation correctly. I'll add that the notation set of samples aren't really much different from the regular set - they sound the same, and don't have trills available either.
I know that Finale power users who also insist on getting not only good notation but also a good recording out of a notation program, have tricks to make the playback beyond what's seen on the page. In the instance of your trills, I think it's quite possible they would add the extra notes required, and then flag them to be invisible. If you can hide things in your score that way with Notion, that would be worth an experiment at least.