The following links are free sources for scores in the public domain.
Remember: Hamline also owns scores you can borrow. You have access to scores from the other CLIC libraries and, possibly, the rest of the world. To find scores in CLICsearch, enter a term -- composer, title, instrument, etc. Then, use the filters on the left (under Tweak it!).
Resource Type > scores
For example:
horses > Resource Type > score
bach > Resource Type > score
voice > Resource Type > score
voice and bach > Resource Type > score