if you use midi in dosbox. you can't capture it with the dosbox capture, but you have to use audacity or something like that.
(as the midi sound isn't generated by dosbox)

Qbix
The File I got by Capturing with DoxBox using Munt is a MIDI file?
The extension is .WAV..
I f I try to reproduce with Audacity, no WAY...
Why?

Qbix wrote on 2020-06-28, 11:05:

if you use midi in dosbox. you can't capture it with the dosbox capture, but you have to use audacity or something like that.
(as the midi sound isn't generated by dosbox)

Sorry Dominus
I don’t want to abuse your patience,but but how can I extract audio from the Roland MT-32 emulator?
is it possible to do that?

Hmm, munt may have, I'm almost sure it has, a way to output as file. Grab the full Munt, not just the driver for that and look around in the settings.
Alternatively, do as Qbix suggested, and record the audio via Audacity or anything else.

I've Audacity
When I'm playing the track on Munt, Mt 32 is on and can reproduce
On Audacity if I play Record (Red button) ERROR/impossible
I've not a Microphone

Then you must select the correct source in Audacity.
Or grab the whole Munt not just the driver.

Holy Shit...Simply I can't.....could you please help me?
i'm not native American/English

@Mark_81: I believe you are confused about something here, which I'll try to explain:
As Qbix wrote, Dosbox delegates playback of midi to the host system, eg Windows. So when you play midi, Dosbox is not playing any music. That's why your recording is empty.
Which means you should record it from windows, not dosbox.
Dominus' advice is valid, munt has an obvious "record" functionality, have you seen it? If you only want to record midi music, this is all you need

Qbix' advice to use audacity has an advantage, through audacity you can record everything that will be output to the speakers.
This means that you can record both the sounds effects played by dosbox and the music played by windows.
The only trick to do so is to record from "stereo mix" device, which is disabled by default. Try to find some youtube video on how to enable it if you really need it, but as I said maybe recording directly from munt is enough for you.

Lets try this

And the output will sound like this: https://www.dropbox.com/s/dooevp70ibl1neu/test.wav?dl=0