Use BackgroundMusicVolume (#892)

Vocaluxe/Base/CBackgroundMusic.cs

@@ -183,6 +183,7 @@ namespace Vocaluxe.Base
 
             _CurPlayer = _BGPlayer;
             //Set a default to have a consistent starting point, use SetMusicSource afterwards
+            CSound.SetGlobalVolume(CConfig.BackgroundMusicVolume);
             _MusicSource = EBackgroundMusicSource.TR_CONFIG_NO_OWN_MUSIC;
             _AddBackgroundMusic();
 
@@ -209,6 +210,11 @@ namespace Vocaluxe.Base
                 return;
             }
 
+            if (!IsPlayingPreview)
+            {
+                CSound.SetGlobalVolume(CConfig.BackgroundMusicVolume);
+            }
+
             if (IsPlayingPreview || _BGPlayer.SoundLoaded)
             {
                 _CurPlayer.Play();
@@ -535,4 +541,4 @@ namespace Vocaluxe.Base
             return _BGMusicFiles.Contains(element);
         }
     }
-}
+}