There are a number of different sounds to cue the user that something has happened:
When a keyboard key is pressed or released, there's a click.
When a mouse button is pressed or released, there's another click.
When the mouse's scroll wheel is spun, there's a whoosh as some menu cells spin past.
When the mouse is wagged back and forth in a 'mouse erase', there's the sound of an eraser.
When a menu motion hits the end of a menu segment, there's a thump, and the motion is stopped temporarily (until the end of the thump, actually).
There are 'burbles' — some light deedle-deedles when AUI is working to move from one thing to another, just to say the computer hasn't gone off for good.
The Calculator has some sounds of its own for 'thinking' when it's asked for a total and for clearing the machine.
And Recordings has a large number of beeps and bumps and whistles and whooshes that can be used to spice up a Playlist or Radio Program.