How do i queue/merge multiple sounds in one file in Java?

So i am trying to find a way how to link two or more sounds together. im not sure how to explain it, but its basicly starting the sound2 while the sound1 is playing after time x. And finally writing this in a file.

I did an example of what i mean in Audacity that you can imagine better

as you can see the sounds can be the same but dont must!

Thank you for every answer

PS: Don't know if this is relevant, but i could do this already without saving into a file, just with playing, with mulithreading and the Thread.sleep(millis) function.