if you don't install a midi device then all you can use is fm synthesis

I think that in DOS a MIDI device needs to be actually connected to the MPU-401 output to have MIDI music. Otherwise it's working (hence, no error), but the MIDI output goes "nowhere" since there is no device at the other end...

From inside Windows 9x, it should work fine, as the drivers can route the MIDI output to the Windows software MIDI synthesizer.

Thanks all for support!
What do you mean Midi device connected? Is it sofware or hardware? Sorry im newbie in retro pc...

In DOS, you need a hardware device (which you don't have by the sound of it).

In Windows, you can use the built-in Windows MIDI synthesizer (software).

Hardware. For DOS you need a real MIDI hardware device connected to your soundcard's MIDI output. E.g. some Roland SC-55, SC-88 or similar. Or one of dreamblaster's new devices:

https://www.serdashop.com/Webwinkel-Product-1 … ule-Bundle.html

This is not so much retro, as it is the way MIDI works. 😀 Except if your soundcard has an onboard MIDI module...

Thanks for all answers... This forum is great!!
Many thanks!