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According to your description, whether you want to enumerate the values of FxProperties? If so I suggest you could try to use RegEnumValueA function to enumerates the values for the specified open registry key.
FxProperties values: The FxProperties registry key holds the system effect APO configuration for a specific audio endpoint device.
Each audio endpoint device has its own key, named after the endpoint GUID.
Under each endpoint device key, the
FxProperties key contains system effect APO configuration.
For more details I suggest you could refer to the link: https://github.com/dechamps/APO
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