All the sounds are packed into one .SND file. A character's .CNS file determines what sound is triggered when a particular action is performed, like special moves, punching, etc.
As for modifying, the only full featured program that I know of is Fighter Factory. I say full-featured because there was another one I tried simply called MUGEN Character Maker or something, and when a .SND file was imported, all the possible sounds were not loaded, so for example, if a character had 40 sounds, only 20 or 25 sounds were loaded. Both programs were not accessible with screen readers, if you are wondering about MUGEN Character Maker's accessibility.

Hi Mata,
that were really cool if you could tell me about that program, I really would love to add or Change some sounds in the games.

Hi.
MUGEN is not a game, rather, it's a fighting game engine where you can create your own fighting games, everything from characters, stages, and even the menus are customizable.
I don't remember where to get it, it's been years since I last touched MUGEN.

I think the only choice you have is to try the different buttons on the keyboard to find out which key does what. That depends on how the keys are configured.
Because I dont know the games you wrote about I can't help you, I'm sorry.
But for the sound modifier try the folling:
https://www.dropbox.com/s/w8t4fvisag0bq … v.zip?dl=1
With this tool, I managed to make the sound of a character of mortal kombat with my own voice! It's so cool!
If you have questions about it, just ask and I'll try to help you.
Have fun!

it was a hard search for me, too. I got another program from a skype user but an error appeared and it never worked. I really was frustrated about that.
Then, I searched myself and found this cool cool program which really made my dream come true! I'm so proud of my own character made with my own voice!