OpenMSX and ePSG or dual/double PSG

If you only want to listen to stereo music on PSG games, I'd suggest you to create a custom machine with stereo PSG sound. Step by step:

1. Go to the folder where OpenMSX is installed and open the machines subfolder inside the share folder.
2. Open with a text editor the configuration file for an MSX computer with stereo PSG sound, like the Toshiba HX-32 for example.
3. Now open the corresponding file for your preferred MSX computer, say, the Panasonic FS-A1WSX.
4. In the Toshiba xml, find the sound subsection inside the PSG section inside the devices section (it should be from line 65 to 70 if your file is the same as mine).
5. Now do the same for the Panasonic xml (it should from line 59 to 61 if your file is the same as mine).
6. Before doing any modification, save this xml in your personal documents folder, inside the OpenMSX folder there should be a share folder and a machines subfolder as well. Just change its name so you can select this machine later (for example, a good name would be "Panasonic_FS-A1WSX_(stereo_PSG).xml").
7. Now replace the appropriate subsection with the one from the Toshiba xml.
8. Save and voilà! You'll have a new machine option, the Panasonic FS-A1WSX (stereo PSG). If you were running OpenMSX or Catapult, restart to see your new machine option.

Of course, I edited the original GT with the new values... still not working.

The MSX is a mono machine, so there is no true stereo music in games. Parn's solution uses a pseudo stereo effect using only one PSG. PSG channel 1 is played center, channel 2 is right (or left?) and channel 3 is left (or is it right?). Of course, this is only possible on an emulator, not on a real MSX.

A few (enhanced) games support dual PSG. But they only use it to have more audio channels available. Take for instance Sky Jaguar plus that now has background music and some speech. Most classic games have been written for single PSG and will ignore a secondary one.

The code below is for an extension for a secondary PSG. Save it as secpsg.xml in your folder %userprofile%\Documents\OpenMSX\share\extensions and a new extension 'General Instrument AY8910 Secondary PSG' will be available.

If you enable vu meters from the openMSX menu (Advanced -> Toys and utilities -> vu meters) you can see it in action. Tested with Sky Jaguar plus and it works fine.

<?xml version="1.0" ?>
<!DOCTYPE msxconfig SYSTEM 'msxconfig2.dtd'>
<msxconfig>
  <info>
    <name>Secondary PSG</name>
    <manufacturer>General Instrument</manufacturer>
    <code>AY8910</code>
    <description>This extension contains a secondary AY8910 sound chip on I/O ports $10-$12</description>
    <type>sound expansion</type>
  </info>
  <devices>
    <PSG id="PSG secondary">
      <type>AY8910</type>
      <sound>
        <volume>21000</volume>
      </sound>
      <io base="0x10" num="2" type="O"/>
      <io base="0x12" num="1" type="I"/>
    </PSG>
  </devices>
</msxconfig>

I didn't know that. Are there any games that exploit this? Maybe even to a level that when something happens on the left of the screen you get a sound coming from the left?

@Grauw I own a Japanese HX-21 and always consider this full channel panning (not a real stereo).