Real scratching in realtime needs not only moving the waveform, but also wiggling a very loose crossfader with just the right timing. With many standard “tricks” you just provide some base noise via moving and accelerating/decelerating or even stopping the waveform, and open the fader for just the right portions of sound to come out as a result.
Controller scratching is possible. But you need some things to know, that “degrade” it in comparison to a realy turntable. It isn’t quite “the same”…
First, those affordable controllers all have no motorized platters with slipthrough. So you have to watch the pc screen with the waveform to know what speed they are moving by themselves when you let go of them, and what their position is, also the feedback of platter rotation vs real waveform shift might not be perfect because of coded in acceleration and deceleration. The feel is also different, with vinly, at least I think by having watched people doing (don’t beat me if I’m wrong) you hold the record, which will slip though the slipmat, while the turntable rotates on - you have that constant drag at your finger, if you let go, the mat will grip the vinyl and rotate on. Platters are loose, and also might have mass rotating on to both directions.
Next the cheap controllers won’t have so very great resolution. When doing advanced scratches, where very slow movement or very fast extreme moves are on, you won’t get the ultra correct and snappy shit like with vinyl. I’ve heard modern controllers are beginning to have better resolution at affordable pricetags, but better watch what you buy if you plan on seriously trying to scratch.
Last but not least: there’s latency in the digital buisiness. If you have audio buffer settings of 15ms on your computer, that means moving the platter will result in 15 milliseconds plus XYZ milliseconds midi-delay and sound card internal and such until you hear your move out of the speakers. That might sound silly, but I know from playing the guitar with software plugins…anything above 5-7ms begins to sound more and more like the fingers are moving through some sticky goo. I bet scratching is very much the same. So you’ll want to make sure you have a controller and system that will allow cool latencies for the scratching business.
With all those shortcommings, I bet the videos you see on YT with people doing cool scratches on cheap controllers are from people…who are very experienced and/or put a lot of time into mastering those devices.
But: scratch action is possible with controllers after all, even with cheap ones, but not really with a mouse unless some 12 year olds want to have some simple fun for 20 minutes and then forget about it the rest of their lives.