M4R is a highly specialized audio file format. This format (full name - iPhone Ringtone File) was developed by Apple's IT giant specifically for the iPhone. This format creates music ringtones for the iPhone. ITunes Ringtone is the main program for opening files with the extension .m4r, and their creation is mainly using Apple iTunes. Formally, M4R files can only be created from songs and other works purchased in the iTunes music store. The size of the created ringtone in the M4R format can be a maximum length of not more than 40 seconds.
MP3 is the most common music (sound) file format. This format was developed by Fraunhofer IIS and Thomson. This format for storing and transmitting music (sound) files in digital form uses signal compression technology. That is why, unlike the previously widespread WAV format, MP3 files (full name - MPEG Audio Layer-3) are much smaller in size, and their sound quality is much higher. The MP3 format was one of the first and most successful sound compression methods. One of the important characteristics of this process is the degree of compression, that is, how much data is transferred per unit of time. Standard MP3 encoding is from 64 to 320 kb / s.