Stereo Tool

I know I can set config file, but I want to set it with the Stereo Tool. I want to use headphone test and ear test at high frequencies with musics.

Could you elaborate a little? I don't really understand what you're trying to ask. If you're asking how you can listen to the high frequencies only, go to "Multiband" and click the last 1 or 2 "Monitor" ("M" or "Mon") buttons.

It is not entirely sharp cutting frequency.

OK, if you want to make it so the frequencies don't cross over or anything, you can go to Configuration > User Interface > and set it from "Basic" to "Extreme Tweaker". Next step, you go to Multiband > Bands > then just pull the sliders on the 2nd and 3rd tabs all the way to the right so they're completely orange, then you should notice the bands look a lot more sharp, not completely, but it's the best you will get.