Disklavier

Help on another topic:
The pre-recorded diskette files we received play too loudly on the
piano.  Turning the volume down to "-10" does not provide sufficient
volume reduction.  

The environmnent we're playing in needs the music to be not so
overwhelming.  

Looking for options:
1)  Is it possible the unit is faulty, and that "-10" should be
significantly reduced ?
2)  Is there any way to modify the prerecorded disk files using a midi
editor (set the volume lower in the midi file)?
3) Other ideas?

Thanks