Find printed music at Lewis & Clark College and other libraries by searching by title, composer, instrument, etc., in Primo, the library catalog, and limiting your results to Scores. You may do this either up front in the Advanced Search with the Material Type drop-down menu, or after you have results, selecting Scores from the Resource Type list under Refine My Results. Scores at other libraries may be request through Summit and interlibrary loan, both free services.
Browsing in person can sometimes be a fruitful way to discover items you didn't know you were interested in. (It's also important to search in the catalog so as not to be limited only to locally available items.) All scores are shelved together under call numbers beginning with M, with music organized by instrument and ensemble size. Here are some of the most useful call numbers for browsing scores at Watzek:
M3 Collected works of a single composer
M6–M179 Music for one solo instrument
M20 Solo piano music
M180–299 Duets
M219 Violin and piano sonatas
M300 Trios
M400 Quartets (500 = quintets, 600 = sextets, etc.)
M1001 Symphonies
M1500 Operas
M1611 Music for one solo voice