The Apple Music API allows an app to search for a song and add it to the users iTunes library, but it does not provide any method to download the song from the cloud to physical storage on the device. In theory, the app could play streamed songs from the Apple cloud, but that creates very unhappy customers if they try to use the app for a game that does not have internet access.
I do keep a watchful eye on the Apple operating system releases and I will add song search as soon as the capability to trigger song download to the device is available.
