Added detailed explanation for the opn2_setScaleModulators() function

#125
stuerp/foo_midi#108

Author: Wohlstand

include/opnmidi.h

@@ -418,9 +418,20 @@ extern OPNMIDI_DECLSPEC void opn2_setChipType(struct OPN2_MIDIPlayer *device, in
 extern OPNMIDI_DECLSPEC int opn2_getChipType(struct OPN2_MIDIPlayer *device);
 
 /**
- * @brief Override Enable(1) or Disable(0) scaling of modulator volumes. -1 - use bank default scaling of modulator volumes
+ * @brief Override Enable(1) or Disable(0) scaling of modulators by volumes. -1 - use bank default scaling of modulator volumes
  * @param device Instance of the library
  * @param smod 0 - disabled, 1 - enabled
+ *
+ * When this feature is enabled, all the modulators will scale together with the volume
+ * that will cuase an effect of sound smoothing. However, it's better to use the CC74
+ * to explicitly control the volume of modulators when it's needed, otherwise using
+ * of this feature causes a lot of problems. It's possible that this feature will be
+ * removed eventually and this function will become useless.
+ *
+ * IMPORTANT: If you develop music player or plugin, or integrate this to somewhere,
+ * suggested to don't add binding to this feature and keep it always disabled.
+ *
+ * Details: https://github.com/Wohlstand/libOPNMIDI/issues/125
  */
 extern OPNMIDI_DECLSPEC void opn2_setScaleModulators(struct OPN2_MIDIPlayer *device, int smod);