This may be an off chance, but in you ff7_opengl.cfg, does it say..
# ff7_opengl-0.7.8b config file
# mod directory
# subdirectroy of mods/ where textures will be loaded from
# does not affect the old external textures feature, those should still go in textures/
mod_path = none
# use shaders, if available and supported
# turn shaders off to use the OpenGL 1.1 backend
use_shaders = yes
# plugins
# a movie plugin is required, the music plugin is optional, but required to make FF7Music work
movie_plugin = plugins/ffmpeg_movies.fgp
music_plugin = plugins/ff7music.fgp
See right there above? The file comes stock like this
#music_plugin = plugins/ff7music.fgp
you have to remove the # symbol to make it work, make it look like this
music_plugin = plugins/ff7music.fgp