I would be very interested in a description of the process that you used to create this.
Audio:
The mechanics of it are actually very simple. I started with the base drum track as a backing track. In my DAW software (I use Cubase, but any DAW will do this pretty easily), I created a track for bass and armed it to record.
Recorded the bass track.
Created a new track for the rhythm guitar. Recorded that.
Created a new track for the lead guitar. Recorded it.
The piano was slightly different in that it was a MIDI track and I used a synth plug-in within Cubase, but otherwise the same thing.
Mixdown Audio for the final product.
Video is just as easy.
Recorded each video track as I played it, so I ended up with 4 separate video recordings.
The video software I use (Magix Movie Studio Platinum 15) lets me load all video recording on their own track along one timeline. Using their Picture-in-picture feature on each video, I resized the windows and placed them as you see in the final video. Loaded the mixed audio track.
The only part that takes any real time is manually syncing the videos. Each video recording also has an audio recording that is perfectly synced to the video from the mics built-in to the camera. The audio quality stinks, but it works very well for sync'ing to the mixed audio. Once everything is synchronized, I mute the audio from the cameras, Do a simultaneous fade-in on all videos at the beginning and a similar fade-out at the end. Render and done!
The bass and guitar parts were all done through the Eleven Rack directly into Cubase. The amp model for the guitars is a Mesa Boogie, through a 4x12 Greenback cabinet into a condenser mic (I forget which one). The bass was through an Ampeg SVT emulation with an Ampeg 8x10 cabinet and the same condenser mic. The piano is a MIDI input directly to Cubase, using Cubase's Halion synth plug-in. I don't remember the exact patch I used, but it was based on a Fender Rhodes studio 88.