Voicemeeter is a versatile "virtual audio mixer" software for Windows*.

Voicemeeter is a versatile "virtual audio mixer" software for Windows*. This is a one-hour webinar covering everything in the Voicemeeter software's manual, for those who would rather watch a video!
*XP, Vista, 7 and 8, both 32 and 64-bit.

Voicemeeter allows two hardware inputs (or more in some cases) to be mixed with system sounds with slider control over each level, and some strip-based processing as well. Output to monitoring devices AND broadcast or recording software can be controlled for each input. I know of no other software offering this much flexibility, and it is free to use, being monetized as donationware - pay what you can according to your means. 

Download the PDF of the manual here, then follow along!
http://vb-audio.pagesperso-orange.fr/Voicemeeter/Voicemeeter_UserManual.pdf

Voicemeeter: http://vb-audio.pagesperso-orange.fr/Voicemeeter/

VB-Audio Virtual Cable: http://vb-audio.pagesperso-orange.fr/Cable/index.htm
http://www.youtube.com/watch?v=Pb7JtF8E85U

I'm trying to tackle a "show opening" issue.

I'm trying to tackle a "show opening" issue.  I'd like to stack an audio file of 12-13 seconds, over a video intro file of 10 seconds, over a live camera.  
The idea being music starts with video and as video completes and disappears the camera video appears while music fades.  I have had some success with this, upon building it, but subsequent uses of the scene only show the camera.
Does anyone have any suggestions as to why this is occurring?
My sources (all global) are video specifying an MP3 (audio only file), a video specifying a silent MP4 (video only) file, and a live webcam.
Any/all feedback would be appreciated.