The Lester S. Levy Collection of Sheet Music is a digital initiative by Johns Hopkins University. As far as I can tell, everything from the physical collection was scanned, except perhaps material published after 1923. It's sad to see "Images are restricted due to copyright and are unavailable for viewing” for many items published after 1923, but there is still a text record for those entries, and the selection decision is mentioned in the site's FAQ and search tips section.
The scans of sheet music collections are available as downloadable .pdf’s, which seems like a good choice for keeping sets of sheet music together. I can’t figure out the resolution of the .pdf images, but they’re quite clear, and seem to be fairly large, with one 4 page grayscale .pdf having a file size of 2.88mb. For black and white images, a choice was made to scan as grayscale, while color printing is scanned in color.
The metadata is fantastic, with notable fields such as the first line of the song and its chorus, as well as a field for listing the “Engraver, Lithographer, Artist”. The naming for items is related to their box # in the archive, which is effective for locating the original artifacts. It is slightly awkward when this same convention is used for browsing the collection, limiting the user to browsing one box at a time. One feature that I really like is the “tours” section, which combines lectures from Lester S. Levy with images from the digital collection, and seems like a great way to show off and activate a digital collection. The only thing lacking is a direct link to the item in the collection from the tour.