Playback should be able to select voices, not just instruments

This request came up in the German forum, see http://musescore.org/de/node/13338

It'd be pretty helpful if for example for a 2 stave S/A+T/B score one could listen to e.g. Bass only.
Currently this requires a full 4 stave SATB score, which then of courses takes twice the space (on paper)

Possible? Feasible? Discussed already?