If you install any Sound Clip in System 7, you will be able to customize your Mac beep just by opening the Sound Control Panel and selecting the Sound Clip you have installed.
Utilities like SoundMaster allow to assign custom sounds to normal Mac operations such as startup, shutdown, insert disk, etc.
To use Sound Clips with the SoundMaster Control Panel, you will first need to convert the sounds you want to use to SoundEdit format. Then place all converted sounds in a new folder inside the System folder, along with SoundMaster.
There are many other applications like MacroMind Director, Adobe Premiere, etc… that can take advantage of high quality sound. It is very easy to install SoundClips in those applications, just follow the instructions on your application’s manual.