There is a wealth of material within this Consortium database. Almost 50,000 instances of sheet music from the Library of Congress are aggregated here. Additionally, the "about" page makes clear the Consortium's purpose as well as the different collections original creators and provenance. There is even a section explaining dublin core standard metadata tags and all the necessary steps to gain approval as a member of the Consortium--a boon to smaller institutions not knowing where to start with digitization and a great way to make sure everything is standardized. I could not find much in terms of linking or interoperability, but the Consortium does allow you to "collect" instances into your own "virtual collection", as well as view other's previously created virtual collection, a fascinating resource and about as close to "web 2.0" as I've seen a curated digital collection get. The search function is also fantastically robust, allowing searching in multiple fields and with several symbol-based search enhancers such as a # to search for prefixs (i.e. lov# returns loving, love, lover, etc.).
Since all of the collections have to conform to dublin core standards, there is a perfectly acceptable and standardized amount of metadata for all instances. Of course, the display of this metadata leaves something to be desired on some of the external sites, which is a problem when you need to move off-site to reach the actual instance. However, the rule of conformity means the metadata will be there, even if it requires a little more searching. The only field that is markedly absent involves metadata about technology and processes used.
I can't say much for the actual instances: for one, they are not actually hosted within the consortium and for another the quality and structure vary wildly depending on the individual collection they are held within. The Library of Congress, of course, has it done up right; I can't say the same for some of the others. There is also nothing about copyright upon the Consortium site itself. One must travel to the individual collection's pages to find this information.
Overall this Consortium is a great resource for sheet music scholars searching for information on a specific piece, as this aggregate seems to collect a whole lot of them--over 100,000! The intended audience is likely either researchers or fans of sheet music or the periods they came from.