I recently had to replace my iPad mini. I restored the mini from the backup file I had created in iTunes from my previous iPad.
When I went to turn on iTunes Match on the iPad I realised there were two ways to do this.
There is a setting in Settings > iTunes & App Stores > iTunes Match
There is also a Settings > Music > iTunes Match
As you may know in Settings > iTunes & App Stores > iTunes Match, the currently used Apple ID associated with iTunes purchases is displayed above the iTunes Match field.
I have two seperate Apple ID's, one for iCloud the other a legacy ID for purchasing.
When I turned on iTunes Match in Settings > iTunes & App Stores > iTunes Match I got the warning asking me if I wanted to change the Apple ID associated with the iPad and that it could only be done once every 90 days.
I cancelled the dialog box, it disappeared and I tried turning on iTunes Match again. This time the warning did not appear. However after a minute or so the switch automatically reverted to the off position.
There was also no activity in Music, usually I would expect to see the iCloud icon and a progress bar.
I checked in Settings > Music > iTunes Match which was also set to off.
I repeated turning on iTunes Match but this time in Settings > Music > iTunes Match. I again got the warning but this time proceeded with the association of the iPad to the account specified above the password field entry in the warning dialog box. (The Apple ID I use for purchasing).
I then went to iTunes on my Mac Account > iTunes in the Cloud > Manage Devices. I removed the reference to what I took to be my old iPad mini and then after a little while my new iPad Mini appeared telling me I would have to wait 90 days to change association again.
Back on my iPad in Music the iCloud icon with progress bar had appeared and everything went as expected with the references to my iTunes Match library appearing to populate the app.
My question is within the above context are the two methods for turning on iTunes Match interchangeable and global or do they invoke the expected Apple ID in different ways pulling the password from different locations? i.e. iCloud and iTunes Stores settings.