Hello,
Based on my use of the AMPLIFI Remote App V 2.50.3 on iOS 9.3.1 both with an iPhone6S and iPad 2 (when logged in with a Line 6 account), I was hoping other can confirm the current limitations I have discovered:
All itunes Music will appear in the Amplifi App, as long as it is on (downloaded to) the iOS Device. All itunes Music purchased (not necessary downloaded) will appear in the Amplifi App, as long as it was purchased in iTunes (note, does not need to be downloaded to the iOS Device), as long as "Settings > Hide Songs Not On Device" is set to off.* Home sharing of itunes Music Library from a PC/Computer is not supported, and will not display that Music in the App at all.
* Note, the 'retrieving tones' ability would sometimes not work on the iPad 2 when playing a music file from the Music Library displayed in the App. This seemed to be able to be worked around, by ensuring at least one song from the itunes library was downloaded to the iOS device, and played to allow a retrieve tones to occur.
If other users could please confirm my experiences above reflect their own it would be appreciated :)