Hello. I am trying to use soundfont with Dosbox on Windows 10 64 bit but the methods I find on the Internet are not working for me.

Here is what I did :
1) Installed Coolsoft Virtualmidisynth
2) Installed a soundfont (Arachno) in Virtualmidisynth
3) To check if it was working, I launched GZDoom and checked the audio menu. I could select the Virtualmidisynth midi player and hear the difference.
4) I installed Coolsoft Midimapper, that allowed me to set Virtualmidisynth as the default midi player.
5) In Dosbox, I used the command "mixer /listmidi" and "midiconfig" to be sure it's using the right midi player

And it does not work in Dosbox. Have I missed something obvious ?