There is only one file type that uses the .MINIGSF extension:
Game Boy Advance Song File
Audio file from a Game Boy Advance (GBA) game; often loaded along with a corresponding .GSFLIB file, which contains a list of songs from the corresponding GBA game; formatted similarly to a .MIDI file.
The MINIGSF file can be ripped from a GBA ROM and played back on a computer using a supporting audio player.
Updated: May 24, 2014