I am not finding a method of selecting an audio input which can "bridge" scenes.

I am not finding a method of selecting an audio input which can "bridge" scenes. I produced a video intro for my broadcast which contained a musical track which played for a few seconds (fading) after the video faded to black. I noted that when upon seeing the video fade and selecting the second scene with live cameras, the scene 1 audio abruptly cut off. I was unable to find a way to include an audio global source which i could keep in all scenes and thereby supply a continuous audio track.
Does anyone have a suggestion to address this issue?

I'm stepping up from Logitech to a Canon HV20 Camcorder which has an HDMI output.

I'm stepping up from Logitech to a Canon HV20 Camcorder which has an HDMI output.  So I'm now shopping for an appropriate video interface card to pull it into my Windows machine for use in my live streaming events.  I would welcome any suggestions from the community on which card to use.  Ideally, I'll be collecting at least 2, possibly 3 such cameras. I'm presuming that the interface cards offload at least some processing from the CPU so I'll want to install a card for each camera. (Unless advised otherwise by an informed community.)