Hi,
Notation Player does only that - plays back MIDI files, with all the various MIDI controllers as they are in the file. What you will hear when compared to playing the same file in other programs will depend on the fact that you need to be using the same MIDI playback device, and this may be the rub here. Some MIDI playback devices (eg. the default GS Wavetable) are not as "nuanced" as other playback devices, and so playback in such a device may sound as if the player is not responding to note velocity.
But Player still doesn't allow editing Note Velocities
ttfn,
Sherry