diff --git a/src/engine/dispatch.h b/src/engine/dispatch.h
index 7e1a56081..ceeb0fbb6 100644
--- a/src/engine/dispatch.h
+++ b/src/engine/dispatch.h
@@ -29,6 +29,12 @@
 
 #define addWrite(a,v) regWrites.push_back(DivRegWrite(a,v));
 
+// HOW TO ADD A NEW COMMAND:
+// add it to this enum. then see playback.cpp.
+// there is a const char* cmdName[] array, which contains the command
+// names as strings for the commands (and other debug stuff).
+//
+// if you miss it, the program will crash or misbehave at some point.
 enum DivDispatchCmds {
   DIV_CMD_NOTE_ON=0,
   DIV_CMD_NOTE_OFF,
diff --git a/src/engine/instrument.h b/src/engine/instrument.h
index abee4223a..f1885225b 100644
--- a/src/engine/instrument.h
+++ b/src/engine/instrument.h
@@ -23,6 +23,9 @@
 #include "dataErrors.h"
 #include "../ta-utils.h"
 
+// NOTICE!
+// before adding new instrument types to this struct, please ask me first.
+// absolutely zero support granted to conflicting formats.
 enum DivInstrumentType {
   DIV_INS_STD=0,
   DIV_INS_FM=1,
diff --git a/src/engine/platform/pcspkr.cpp b/src/engine/platform/pcspkr.cpp
index 5f57f31ae..f485bca8a 100644
--- a/src/engine/platform/pcspkr.cpp
+++ b/src/engine/platform/pcspkr.cpp
@@ -122,7 +122,11 @@ void DivPlatformPCSpeaker::beepFreq(int freq) {
     gettimeofday(&ie.time,NULL);
     ie.type=EV_SND;
     ie.code=SND_TONE;
-    ie.value=freq;
+    if (freq>0) {
+      ie.value=chipClock/freq;
+    } else {
+      ie.value=0;
+    }
     if (write(beepFD,&ie,sizeof(struct input_event))<0) {
       perror("error while writing frequency!");
     } else {
diff --git a/src/engine/playback.cpp b/src/engine/playback.cpp
index 511e55e17..acc4e7607 100644
--- a/src/engine/playback.cpp
+++ b/src/engine/playback.cpp
@@ -42,6 +42,7 @@ const char* notes[12]={
   "C-", "C#", "D-", "D#", "E-", "F-", "F#", "G-", "G#", "A-", "A#", "B-"
 };
 
+// update this when adding new commands.
 const char* cmdName[DIV_CMD_MAX]={
   "NOTE_ON",
   "NOTE_OFF",