I would like to add a solo soprano stave to my sheet, can anyone tell me how to accomplish this?
I'm also using Garritan Personal Orchestra 4 and would like this stave to play back with a solo voice sound.
Just go to window tab and find the score manager. In the score manager you can add, delete, rename, rearrange, and do so much more to all the staffs. There you can add a soprano staff and rename it solo soprano. If you want a sound from the Garritan library you can set it in the score manager too.
Edit: This how to configure the Garritan library. It is directly taken from the link in the comments.
To assign Finale's included Garritan sounds to score Instruments manually
Choose MIDI/Audio > Play Finale Through Audio Units.
Choose Window > ScoreManager and ensure one of the available Sound Maps are selected under the Device column for all the instruments (e.g. Garritan Instruments for Finale for the Garritan sounds). These Sound Maps link your score instruments to a Audio Units device installed on your computer, such as the Garritan sounds. When a Sound Map is selected, Finale automatically loads its library of sounds into the Aria Player, which is also loaded into a Bank in the Audio Units Banks & Effects dialog box.
Under the Sound column, select the desired playback sound. Finale assigns the sound to the Instrument, automatically using the next available channel and bank.