I am writing for a Euphonium and the program defaults (I guess) suggest that the instrument cannot play higher than an F4… how can I override that so I can hear it? Or is that a sound bank issue?
The out-of-range notes don’t affect playback, you can switch them off (View>Note and Rest Colors) and write whatever you want. If a high note really doesn’t play back it’s because your euphonium patch doesn’t contain that note.