What is a m4r file and how do I open a m4r file?
M4R files are custom iPhone ringtones created with iTunes. They can only be created from songs purchased from the iTunes music store that allow ringtone creation, and are automatically transferred to the iPhone when the phone is synced with the computer using Apple iTunes. iTunes imports the .m4r file into the phone's database and will put it in the Ringtones library as well. After that connect the iPhone to computer and in iTunes drag the ringtone and drop it on your device. In iOS version 5, Apple introduced new Tone Store, where users can buy ringtones for their iPhones. Ringtones are downloaded to phone immediately after payment is processed. The maximum length of M4R ringtone is 40 seconds.
Relevant m4r file links:How to open m4r file on Youtube
How to open m4r file on Wikipedia
How to open m4r file on Microsoft.com