MOD is a sound module format used to store music tracks and uses a .mod filename extension. It features a collection of sample instruments, and the samples are assigned to varying music tracks. The sound samples are opened, depending on score notes. Today, MOD can be opened using various audio tracking programs.
M4A is a filename extension for AAC container format and is developed by Apple Inc. M4A music is bought on the iTunes Store and does not come with DRM protection. In terms of quality, M4A is better than MP3 because it is lossless but still compressed. This means that it occupies less storage space and doesn’t lose quality over time.
iTunes Apple QuickTime Player VLC Windows Media Player