diff --git a/audio/engine_1.asm b/audio/engine_1.asm
index 8b30fb1a..24c93c9a 100644
--- a/audio/engine_1.asm
+++ b/audio/engine_1.asm
@@ -831,7 +831,8 @@ Audio1_note_pitch:
 	bit BIT_PERFECT_PITCH, [hl] ; has toggle_perfect_pitch been used?
 	jr z, .skipFrequencyInc
 	inc e                       ; if yes, increment the frequency by 1
-	jr nc, .skipFrequencyInc
+	jr nc, .skipFrequencyInc    ; Likely a mistake, because `inc` does not set flag C.
+	                            ; Fortunately this does not seem to affect any notes that actually occur.
 	inc d
 .skipFrequencyInc
 	ld hl, wChannelFrequencyLowBytes
diff --git a/audio/engine_2.asm b/audio/engine_2.asm
index 8783c4c6..2d15f7bb 100644
--- a/audio/engine_2.asm
+++ b/audio/engine_2.asm
@@ -842,7 +842,8 @@ Audio2_note_pitch:
 	bit BIT_PERFECT_PITCH, [hl] ; has toggle_perfect_pitch been used?
 	jr z, .skipFrequencyInc
 	inc e                       ; if yes, increment the frequency by 1
-	jr nc, .skipFrequencyInc
+	jr nc, .skipFrequencyInc    ; Likely a mistake, because `inc` does not set flag C.
+	                            ; Fortunately this does not seem to affect any notes that actually occur.
 	inc d
 .skipFrequencyInc
 	ld hl, wChannelFrequencyLowBytes
diff --git a/audio/engine_3.asm b/audio/engine_3.asm
index 404e6e7c..2f1bbf96 100644
--- a/audio/engine_3.asm
+++ b/audio/engine_3.asm
@@ -831,7 +831,8 @@ Audio3_note_pitch:
 	bit BIT_PERFECT_PITCH, [hl] ; has toggle_perfect_pitch been used?
 	jr z, .skipFrequencyInc
 	inc e                       ; if yes, increment the frequency by 1
-	jr nc, .skipFrequencyInc
+	jr nc, .skipFrequencyInc    ; Likely a mistake, because `inc` does not set flag C.
+	                            ; Fortunately this does not seem to affect any notes that actually occur.
 	inc d
 .skipFrequencyInc
 	ld hl, wChannelFrequencyLowBytes