i am using this program called nero to edit some sound files, but as far as i can tell there is no way to have to sounds overlap and play at once; you can only add sounds or play around with the way they sound.
is there a way to make sounds overlap with nero?
if there isn't, is there a free program that will let me do it?

I'm guessing the songs are overlapping and then being put in a video?

You can use audacity (found in the software sticky) to do the music editing and then save the sound file and bring it into nero.

Audacity would be a great choice, but if you want to have a "Garageband experience" (like I did), you can try Mixcraft, or some other music editor with loop things, but I think the best choice would be Audacity.

Audacity

Mixcraft

Although Mixcraft is not free, but you can use if for 7 days, then you can use Audacity to record the loops and convert them to .mp3 like I did lol.