IMHO, musically intelligent virtual performers are the future of expressive music using these libraries. The virharmonic approach is moving in the right direction. I'm not sure, from their documentation on the website, how user-configurable their performances are. That's the key component in any of this. The composer needs to be able to design or sculpt a performance style that can be saved as a performance preset and then applied to the music on playback. There are some real issues with being able to do this in real time to achieve an improvisational performance because some features of the music that you'd want to be made expressive are only known after they've occured, such as melodic peaks and troughs, the first pitch in a repetition, etc. That means the software would need to be able to look into the future. Quantum computers perhaps? ;-). This, of course, is completely possible when treating a pre-composed MIDI score by introducing an event delay in analyzing the score, effectively allowing the software to look into the future.
We're on the cusp folks... stay tuned for interesting times to come using these technologies.
Kenneth.
"Stirred with poetry, standing in ritual, completed with art and music." - Li Po
Kenneth Newby ——— Composer-Artist —— Flicker Art Collaboratory
Music Composition — Computational Poetics — Visual Art — Media Art