hi guys, I am responding on behalf of Harvest Media. We provide the backend system and management tools for delivery and management of production music + we have robust API that many of our clients build off to create custom music solution.
Some great examples of libraries that use our platform are:
http://www.bigbangfuzz.com
http://www.deepeastmusic.com
http://www.thelicenselab.com
http://www.soundpocketmusic.com
there are many more as well
all of these clients use our API and management system and have either used their own developers or us to implement their outcomes.
We actively assist designers in using our API and can answer any questions you might have in relation to getting up and running.
You or your designers can reach out to angus@harvestmedia.net to find out more.
All the best