UPDATE: Apple have marked this feature enhancement as a duplicate of 7040203
Filed as Radar #10286028
Currently, apps have to jump into the iTunes Store app on iOS when prompting the user to purchase songs & video.
The user taps a "Buy in iTunes" button in the third-party app. This jumps into the iTunes app. The user must then tap the Buy button in iTunes and then enter their Apple ID password.
To reduce the number of user-actions and potentially increase on-device music purchases, Apple could create an in-app purchase API for music, similar to standard in-app purchases.
A native search API for iTunes could be created, which would mimic the current JSON API. A standard system UIViewController could be used to display search results and handle the purchasing experience. Songs downloaded would be added to the user's Music / Video apps.