I have a score set up with horns, guitar, bass, drums. No matter what I do, when I press keys on my MIDI controller I hear drums. Now the score itself plays back fine. Each track is properly output...
I use Reaper for arranging drums, etc. Sometimes I use VSTis that use GM map, sometimes a VSTi with different mapping. But either way, I always know what notes correspond to what pieces of the drum...