I'm not sure what you mean by that. You can't change the sound effects with the game, if the sound effects are really shitty, you could redownload the game (save your profile folder and score123 file so you won't have to do everything over again.)
If you want the sound effects on their own, turn the BGM volume off.
If it comes up crappy when you see the playback from a recorder, get a better recorder.If you got and eng. patch of TH 12.3, you going to see a button that saids "custom" or maybe custome with E in your touhou 12.3 file or maybe open touhou and scroll down and you'll see a icon that saids "Config" and just open it and they'll have a letter said something thats near BGM (I don't have an english patch so,just risks it :3).