Remove old comment about RPN messages sent by Logic, clean up the exp…

…lanation (surge-synthesizer#7264)

src/common/SurgeSynthesizer.cpp

@@ -2012,38 +2012,18 @@ void SurgeSynthesizer::sendParameterAutomation(long index, float value)
 
 void SurgeSynthesizer::onRPN(int channel, int lsbRPN, int msbRPN, int lsbValue, int msbValue)
 {
-    /* OK there are two things we are dealing with here.
-
-       1: The MPE specification v1.0 section 2.1.1 says the message format for RPN is
+    /* The MPE specification v1.0 section 2.1.1 says the RPN message format for MPE Configuration
+       Message is:
 
           Bn 64 06
           Bn 65 00
           Bn 06 mm
 
        where n = 0 is lower zone, n=F is upper zone, all others are invalid
        mm=0 means no MPE and mm=1->F is zone.
-
-       So you would think Roli Seaboard would send, since it is one zone
-
-          B0 64 06 B0 65 00 B0 06 0F
-
-       and be done with it. If it did, this code would work.
-
-       But it doesn't. At least with Roli Seaboard Firmware 1.1.7.
-
-       Instead on *each* channel it sends:
-
-          Bn 64 04 Bn 64 0 Bn 06 00
-          Bn 64 03 Bn 64 0 Bn 06 00
-
-       Which seems unrelated to the spec. But as a result, the original onRPN() code
-       means you get no MPE with Roli Seaboard.
-
-       EDIT: Those aren't coming from Roli, they are coming from Logic, and now that we correctly
-       modify and stream MPE state, we should not listen to those messages!
     */
 
-    if (lsbRPN == 0 && msbRPN == 0) // PITCH BEND RANGE
+    if (lsbRPN == 0 && msbRPN == 0) // pitch bend range
     {
         if (channel == 1)
         {
@@ -2058,19 +2038,19 @@ void SurgeSynthesizer::onRPN(int channel, int lsbRPN, int msbRPN, int lsbValue,
     {
         mpeEnabled = msbValue > 0;
         mpeVoices = msbValue & 0xF;
+
         if (storage.mpePitchBendRange < 0.0f)
+        {
             storage.mpePitchBendRange = Surge::Storage::getUserDefaultValue(
                 &storage, Surge::Storage::MPEPitchBendRange, 48);
+        }
+
         mpeGlobalPitchBendRange = 0;
+
         return;
     }
-    else if (lsbRPN == 4 && msbRPN == 0 && channel != 0 && channel != 0xF)
+    else // we don't support any other RPN message at this time
     {
-        /*
-        ** This is code sent by Logic in all cases for some reason. In ancient times
-        ** we thought it came from a Roli. But since we changed the MPE state management so
-        ** from 1.6.5 onwards do this:
-        */
         return;
     }
 }