human effect on playback
guitar pro has an interesting feature which gives a human feel to the sound on playback. The expressiveness is created by giving a delay to the lead note to make it better heard over the accompaniment. This usually only on the first note of each bar but may be on the others too. The length of each delay may be increased and the speed of the whole piece can be a little or a lot rubato. Perhaps this effect can be coded into the exported midi file.