Device not appearing on win8 device list

Hi Matt, the quickest test you can do to check if VirtualMIDISynth is correctly installed and available is to open its configurator.
On Win8 you should have a tile named "Configure VirtualMIDISynth", otherwise look for VirtualMIDISynt_configurator.exe into C:\Windows\SysWOW64\System32\VirtualMIDISynth or C:\Windows\System32\VirtualMIDISynth folder.

Open configurator and switch to MIDI Mapper tab. The combobox "Windows Media Player default device" will show all the MIDI output devices registered on the system; VirtualMIDISynth should appear there.
If not then something got wrong during setup, please let me know and we'll investigate further.

Otherwise something is going wrong in your software.
Which language is your software written in?
Here you are some samples on how to enumerate the MIDI Out devices registered on the system:

C++: http://home.roadrunner.com/~jgglatt/tech/lowmidi.htm
C#: http://www.pinvoke.net/default.aspx/winmm.midioutgetdevcaps

Tried both on a Win8 system and they both detect VirtualMIDISynth correctly.

You could also try a well-known MIDI player like VanBasco, which is known to work on Win8 too (despite the fact it was written at Win95 era...!).

Matt wrote:

I think the issue is that it doesn't register a class compliant device

No it doesn't, because it's not a DirectX device but an "old-style" user-mode multimedia device.
The former is much more difficult to implement and, also, the DirectX layer adds lot of latency.

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