Basically a guitar riff is fed to 2 effect chains each chain contains an amp with different settings (go for different amps/settings so you have two really different sounds). Sequenced gates were used to 'switch' between the two amps in sync with the riffs tempo. What the gates do is to lower the output volume from one of the amps and raise the other (so you switch between the two timbres). You can use automation for this instead of sequenced gates.
I am sure I have a few more. I am doing a disk cleanup at the moment, that is how I found these.
People tend to think of "feedback" as the horrible annoying squeak that you get with microphone-speaker feedback. But it is much more than that: any system where the output or part of it is feedback to the input is a feedbacking system.
Some DAWs allow the setup of feedback routes. Stick some effects on the chain and you can get some pretty interesting results. Maybe others will listen to these and decide to experiment. Main things are: 1) Always keep your hand close to the control for the feedback volume and be ready to pull it down. 2) Always stick a limiter in the master channel.