Jade, if I give you the photos or images, you can superimpose them all together? How about the "original" plus cable a plus cable b (three images)?
I do think you're going to need a good way to sync the recordings.
Here is the old school way the "2 pop". You're going to have to recreate a file that has a short burst tone before the song starts. In a waveform editor you can the place the pop on the same place time-wise by lining up the bursts. It should give you a reference to work with at least.
In video/film a one frame burst is often used to sync picture and non timecode audio and going way back the "clapper" slates were used to sync sound to picture.
I made a short clip that you can use here to see if it will work for you.
(using a short snip from the wonder full Pharoah Sanders track "the creator has a master plan" from the priceless collection cd that everyone should run out and buy)
Your Big File
Again I think you should do multiple recordings of the individual cables to
see how much noise and randomness is in the graphics.