Random Events

My game is about a haunted manor.
In the manor, a spooky BGM plays.
So what I'm thinking is to make the ambience more unsettling. I wanted to throw in some random events that plays it's own SE/BGS. For example, event 1 plays door creaking SE in a totally random time.
The same goes to other random events.

The thing is, I'm uncertain on how to do so.

I did this with a parallel process. Start by having it select a random number and store it as a variable (it's an option under control variables). Then use a conditional branch and set one for each choice of the random variable, and in each one use the command wait(insert frames here) then the SE you want to play.

What you do is you use different values for wait in each conditional branch. So if the random value was 0, it might be wait(200) then the SE, but if the random value is 1, it might be wait(600) then the SE. And so on.

make the events always happen, but use the random generator inside control variable to determine if the player should get anything or if the event ends itself without any other command.

For random wait, I'd prefer script call
Then followed by play SE.

You can change the random waiting interval. On my example it's between 60 frames (1 second) + 180 frames (3 seconds), makes it the SE will be played randomly next 1 second at minimum or 4 second at maximum.