My friend wants to do this and asked me for ideas, im not sure how to go about doing it so im asking here.

I was wondering, what is the best way to record audio commentary on a video live as its happening? Mostly in relation to video game footage.

What would be a good way to do it if you are using something such as FRAPS to record the game video on the same system you are playing it on? (and thus would need to record the commentary on the same system at the same time as well). Shame I can't use virtualdub for the initial capture in this situation since it can't capture live onscreen footage like FRAPS can.

What about if you are playing it on a different system than the PC (such as using a Dazzle to capture video from an external source) but still using the PC to record your commentary? Typically I use VirtualDub for my capture software of choice (Didn't even install the software that came with the Dazzle for him) unless there is a better option for something like this?

I don't need to capture everything to a single compressed file since I would be able to mux everything together later, but if there are multiple audio tracks (if any of the methods record the gameplay's audio and the commentary separate) I would need to know how to combine them together.

He wants to record his reactions as it happens, which is why he wants to record his commentary at the same time as he is playing, and I also know nothing about timing so I wouldn't be able to time his commentary track correctly if it was recorded separately.