diff --git a/Makefile b/Makefile
index dc39c65..7c1915a 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 all: xm_player.elf
 
-OPT = -O2
+OPT = -O1
 
 MAKEFILE_PATH := $(patsubst %/,%,$(dir $(abspath $(firstword $(MAKEFILE_LIST)))))
 LIB ?= $(MAKEFILE_PATH)/dreamcast
diff --git a/src/interpreter.cpp b/src/interpreter.cpp
index cbaec2f..89ef1cd 100644
--- a/src/interpreter.cpp
+++ b/src/interpreter.cpp
@@ -249,10 +249,12 @@ void interrupt()
       break;
     }
     */
-    if (state.channel[ch].keyon == 255) {
-      wait(); aica_sound.channel[ch].KYONB(1);
+    if (state.channel[ch].keyon > 128) {
       state.channel[ch].keyon -= 1;
     }
+    if (state.channel[ch].keyon == 128) {
+      wait(); aica_sound.channel[ch].KYONB(1);
+    }
   }
   wait(); aica_sound.channel[0].KYONEX(1);
 
@@ -261,7 +263,7 @@ void interrupt()
   }
   for (int ch = 0; ch < 64; ch++) {
     int keyon = state.channel[ch].keyon;
-    if (keyon != 255 && keyon != 0) {
+    if (keyon < 128 && keyon != 0) {
       state.channel[ch].keyon -= 1;
     }
   }