Have the terminal tell you when done
Let's assume you give your computer a task that might take a while, like downloading a file. You want an acoustic signal that tells you when it's done.
In the terminal, that's rather easy. Just add the command with two ampersands. Test it like this:
$ ls && say 'I am ready'
In the above example, I'm using the MacOS command say, to make it speak. If you want to keep it simple, or use it via ssh on a server, you can send the ASCII beep signal like this.
$ ls && echo -ne '\007'