code: public void setSoundVolumeFromPreferences(final String preferences, final String preferenceName,
              final float defaultValue) {
          musicPreferences = preferences;
          soundVolumePreferenceName = preferenceName;
          setSoundVolume(readFromPreferences(preferences, preferenceName, defaultValue));
      }
docs: Sets the current sound volume according to the values stored in preferences. Mostly for internal use.
  
  @param preferences path to the preferences. Will be set as global music preferences path.
  @param preferenceName name of the volume preference.
  @param defaultValue used if preference is not set.