• VGMTool 2
• Winamp
• The VGM Winamp input plugin
• A wave editor which can load and show WAV files, zoom in, and tell you the exact position. You could try:
  • Cool Edit 2000 (commercial, free trial)
  • Any other suggestions?

You need to install Winamp, and then the input plugin, but you probably already did that. Open Winamp, and press Ctrl+P to open the Preferences window. Choose Output from the Plug-ins branch, and select the Nullsoft Disk Writer plug-in. If you don't have it, you can get it from the Winamp website, but it should be included in all recent versions of Winamp.

Press the Configure button to choose where to create the file; note that it will be quite large, probably between 10 and 100MB depending on the recording length (it'll use 172KB per second, that's 10MB per minute of audio). Don't worry, you'll delete it in a minute.

Now close the preferences window, and load your VGM file (I like to drag-and-drop it onto Winamp's main window, but you could double-click it or use the Load button). It should play the file quickly, and you won't hear anything, because it's writing the audio to a WAV file instead. When it finishes, go back to the plugin window and choose the output plugin that you were using before (probably Nullsoft waveOut plug-in or Nullsoft DirectSound plug-in), so you can listen to music again.

Hint: Make sure the Equaliser, and any DSP plugins you might have installed, are turned off. They will mess with the output, you don't want that.

This is the slowest and most difficult part of the process. Open your newly-created WAV file in your wave editor, and zoom out fully. The music will be one of three types:

1. A single non-looping track, eg. Alex Kidd title screen music:
   
   1. Stuff before the music starts
   2. The music you want
   3. Stuff after it finishes

   Download this VGM file

2. A simple loop, where when the music finishes it goes back to the start, eg. Alex Kidd in Miracle World level 1:
   
   1. Stuff before the music starts
   2. The music you want
   3. The same music repeated
   4. The same music repeated again

   Download this VGM file

3. An introduction, which leads in to a looping section, eg. Wonder Boy III "The Monster's Lair"
   
   1. Stuff before the music starts
   2. Introduction
   3. Looped section
   4. The looped section repeated
   5. The looped section repeated again

   Download this VGM file

You need to find the exact position of two or three dividing lines between sections:

• The Start - everything before this will be discarded
• The Finish - everything after this will be discarded
• The Loop point - the start of the looped section. Type I doesn't have a Loop point, and for Type II it's the same as the Start point.

You need to find out the sample number for these points; if your wave editor can't display that, you can multiply the precise position in seconds (with decimal places) by 44100, eg. 8.600s × 44100 = 379260 samples.

Here's the edit points I used for the Type III wave above:

Start: Loop: Finish:

The best way to tell if you've got the loop and end points in the right place is to play the wave from both points, and listening to see if they sound exactly the same (because it's normal for the waveforms not to be identical); Cool Edit 2000's Cue List is useful for this.

Here are the edit points for all the example VGMs available to download above, so you can create the WAVs and see for yourself:

When finding these numbers for your own VGMs, write these numbers down (or enter them in VGMTool) as you go.

Hint: While you don't have to be absolutely precise, you may have minor sound problems, often with the PSG noise channel, if you choose a point after the exact position, so try to get as close as you can without going past it.

Load VGMTool 2, and drag-and-drop your VGM file onto it. Enter the edit points you found in the Trimming groupbox. If you want the file to include looping (ie. if it's Type II or Type III), check the Include looping box. Then click on Trim to create a trimmed, optimised and compressed VGZ file in the same folder as the VGM; the program will tell you the filename.

"Optimised"? How? Isn't that step 4?

Well... the vast majority of games have a simple sound engine, because of the limited CPU and RAM available; so simple, in fact, that a lot of the writes to the sound chips are unnecessary. For example, if the chip is playing 440Hz on tone channel 1, telling it to play 440Hz on tone channel 1 is unnecessary as it's already doing that. So that second write can be discarded. Or, if it's set to 500Hz and then 440Hz with no time in between, the first one is unnecessary. Or, if it's told to wait for 1/60s, 10 times in a row, that can be converted to a single command to wait for 1/6s. There's more examples of this. So that's what the optimisation does - it removes unnecessary data from the file, making it much smaller. This is done while trimming.

What's that "Round times" button?

Well... if the file was logged as frame-accurate using Meka then the exact correct edit points are multiples of 735 (for a 60Hz emulated system, 44100 ÷ 60 = 735) or 882 (for 50Hz). If the file has its Playback rate included in the VGM header, this button will do the rounding for you. The rounded times should be close to the times you found; for the example Type III above, the rounded times (shown in the screenshot above) are only 6, 7 and 2 samples out respectively. You should check these rounded times in your wave editor, to see where they actually are; if they are not right, don't use them! This feature seems to usually not work well with VGMs created by Dega.

You should listen to the output VGZ file in Winamp to check that it sounds right, particularly around the edit points (start, loop, finish). If it doesn't, go back and check the edit points again. If it does... well done!

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