Hi,
Notation Player doesn't support individual staff controls. However, your musicians may be interested in Notation Musician, as it has individual controls (mute/solo/volume) per-staff, and also has a really nice Practice Setup feature, where they can set up practice loops with lots of different parameters. There's a fully-functional 30 day trial version at
www.notation.com/Download.php We have "group buy discount" options available if they're interested.
ttfn,
Sherry