Nice project. You must realize that MIDI is absolutely awful at describing 'real' music. For a keyboard player, it might be sufficient to specify pitch and duration, using equal temperament, but for a wind player or especially a string player or singer, most of the stylistic information is missing. This is why a MIDI rendering of a solo violin piece (Bach's Chaconne, for example) or a flute piece is flat and mechanical.
I looked into inventing a replacement for MIDI, where you could specify the attack -- which is highly variable for most instruments -- and the way the sound evolves over time. However, it became apparent that even for 'simple' music, there were simply too many variables. It was easier to just learn the instrument. ;-). I am just an amateur flute player, but I can vary the note attack in 10 or 15 different ways, and change the way the sound developed, including adjusting the timbre during the note's elaboration is several more. A professional can do a lot more.
Professional musicians can play in strict time, of course. However, for many types of music, such as Chopin, the controlled deviation from strict time is an important performance criterion.
