If you're playing the classic PC version of Grand Theft Auto: Vice City and notice that the radio stations or MP3 custom tracks are too quiet (or completely silent) while sound effects and dialogue work fine, you're likely dealing with a common audio initialization issue. The solution involves a specific console command.
I was trying to set the mood. I had the sniper rifle, the drugs, the unlimited ammo—everything a budding criminal empire needed. But the silence was deafening. ail set stream volume 8 gta vice city fix
You must do this every time you launch the game. For a permanent solution, use the next fix. If you're playing the classic PC version of