Try implementing sustain stuff

src/synth/fluid_voice.c

@@ -321,6 +321,7 @@ fluid_voice_init(fluid_voice_t *voice, fluid_sample_t *sample,
     voice->mod_count = 0;
     voice->start_time = start_time;
     voice->has_noteoff = 0;
+    voice->ignore_sustain = 0;
     UPDATE_RVOICE0(fluid_rvoice_reset);
 
     /*
@@ -612,6 +613,15 @@ fluid_voice_calculate_runtime_synthesis_parameters(fluid_voice_t *voice)
         int dest_gen_index = mod->dest;
         fluid_gen_t *dest_gen = &voice->gen[dest_gen_index];
         dest_gen->mod += modval;
+
+        // issue blablabla: If a modulator is in use, which responds to CC64 and intended to manipulate the release envelope, this voice should not be sustained,
+        // to allow the modulator to achieve its desired behavior while the sustain switch is being depressed.
+        if((mod->src1 == SUSTAIN_SWITCH && mod->flags1 & (FLUID_MOD_CC | FLUID_MOD_SWITCH))
+            || (mod->src2 == SUSTAIN_SWITCH && mod->flags2 & (FLUID_MOD_CC | FLUID_MOD_SWITCH))
+            && (mod->dest == GEN_VOLENVRELEASE))
+        {
+            voice->ignore_sustain = 1;
+        }
         /*      fluid_dump_modulator(mod); */
     }
 
@@ -1364,7 +1374,7 @@ fluid_voice_noteoff(fluid_voice_t *voice)
         voice->status = FLUID_VOICE_HELD_BY_SOSTENUTO;
     }
     /* Or sustain a note under Sustain pedal */
-    else if(fluid_channel_sustained(channel))
+    else if(fluid_channel_sustained(channel) && !voice->ignore_sustain)
     {
         voice->status = FLUID_VOICE_SUSTAINED;
     }

src/synth/fluid_voice.h

@@ -105,6 +105,7 @@ struct _fluid_voice_t
     /* rvoice control */
     fluid_rvoice_t *rvoice;
     fluid_rvoice_t *overflow_rvoice; /* Used temporarily and only in overflow situations */
+    char ignore_sustain;
     char can_access_rvoice; /* False if rvoice is being rendered in separate thread */
     char can_access_overflow_rvoice; /* False if overflow_rvoice is being rendered in separate thread */
     char has_noteoff; /* Flag set when noteoff has been sent */