Combining songs to make a duet.

[Amberpamber]

Is there a simple way to combine 2 recordings so they sound like a duet/group singing?

[how.we.operate.]

There are plenty of audio editors out there where you can simply take two tracks, adjust them, and play at the same time as if it is a duet.
Biggest issue with saying how so depends on the platform/computer you use.
Macs - come with Garageband. Here you just make 2 separate tracks for each part and move them around, adjust volume, etc until it is just right. There are many other programs too.
Windows - you can find many audio editors for free as well, just be careful what you are downloading
Online - there are also ones that you can upload your files and mess with online such as http://www.aviary.com/online/audio-editor

After editing, you normally have to export/save as a new file.