Mortal Kombat questions?

Okay so here's the question when your playing Mortal Kombat 3, Trilogy, or UMK3 and your doing brutalities on a fighter does the speed increase of it goes faster if you press the buttons fast enough or what? Im asking because I see people play Mortal Kombat 3,maybe was one of them, UMK3, and Trilogy and they do the brutalities really fast while others do it slow on youtube. Use to have Mortal Kombat 3 and 2 for sega genesis and I just want to know. Five stars for best answer. Thank you. I appreciate it for everybody's answer. I have Mortal Kombat 9 for PS3 to let you know so I know brutalities doesn't have to do with the game even though its taking place from Mortal Kombat 1,2, and 3. Beaten story mode. Extra info.