Recording song directly from playback

So I was searching for 2 days but couldn’t find a way to do this. How can I record voice for a certain period of time and then, w/o pausing the record session or cutting it, play some song while simultaneously recording it in the same record session as the one I was recording my voice to? I’ve heard this can be done in SoundForge although I couldn’t find a way. I’ve also written to Sony but got no reply yet. Thanks community.
Answer #1
I use to use Audacity for this; however, it has not been very well maintained lately.
You can try the beta and see if it works for you.
http://audacity.sourceforge.net/
You can also do this with Adobe Audition.
Answer #2
Well I’ve also got audacity but still doesn’t know how to do it