Scores are on the 4th floor of the BU Library. Look at the map at the bottom of the stairs for the exact location.
Scores start either with M, MM, ML, or MT. On the shelf, the "M" call numbers come first, and are ordered from low to high based on the number after the M.
For example, the following call numbers are ordered from first to last:
Don't worry about what the numbers mean, just note that they are ordered from low (M2) to high (M177)