Rendering Microsoft Gm Wavetable

I made a tune using Windows built-in Microsoft Wavetable GM synthetizer.

In order to render it to WAV, I have tried the new realtime mode which claims to be able to “record what you hear”, MIDI included, but it fails to record the song which results in a completely mute WAV file.

is there a reason for this? and a workaround?

fast solution found: adding a LineIn Device to the master track will make realtime mode work as intended, regardless of if you set the instrument mode to “Ext. MIDI” or “LineIn Ret”!