Did you have a headset or some other sound device plugged in previously?
Q:Why is there no sound in the game? Why is the music playing from a different sound device than the game sounds?
A:You need to configure the sound and/or MIDI device.
Run .\FF7Config.exe as Administrator
In the SOUND tab, select the 'Sound Driver'
In the MIDI tab, select the 'MIDI Driver' and the 'MIDI Data'
Click OK to save the settings
Open the Volume Mixer
Adjust the volume for the playback device, applications and FF7 executable