#1
Hello fellow musicans i got an Idea for a recording that is for 2 guitarists, but sadly im not in a band right now so i wonder if you know how some people can record guitar 1 and then guitar 2 but use both the videos in one so you hear both riffs att the same time?
#2
The absolute bare-bones way to do this would be record each performance with a webcam/phone or similar for a video, and to use Audacity or similar for the audio. Do this twice, so that you have two videos and two audio files. Then use a video editing software that support multiple screens to stick them all together. If you are on a Mac you can use iMovie, or on Windows I know Sony Vegas can do this but it is't free. As far as I know there are no free ones on Windows that can do this but I might be wrong.

It would be infinitely easier if you were just doing audio so if the video isn't absolutely necessary then just record multiple takes in Audacity and layer them up. If you really wanted you could then take the finished audio track and record a silent video of yourself playing along to the track, then stick the video over the audio and you have a very simple music video.

This is all assuming you don't have a DAW or interface which from the question I am assuming you don't.