ResEdit is a utility from Apple that lets you edit the resources of Mac
files.  (Hence the name.)  You will need it if you want to patch games
or extract beep sounds.  You can severely damage your software this
way, so you really shouldn't use it unless you more or less know what
you're doing.  (And even if you do, it's a good idea to use it on a
copy of the file.)

ResEdit can be ftp'd from
<ftp://ftp.support.apple.com/apple_sw_updates/US/Macintosh/Utilities/>.