> Are these rules same in all software or knob behaves slightly different everywhere?

They're different everywhere.

My own opinion is that on-screen knobs for audio-type work can be fine as long as one can grab any part of the knob with the mouse and adjust it by moving the mouse up and down (er...well, physically forward and back).

But things are not always this way so it seems that opinions vary.

Yeah, I see how it can be confusing for novices. But learning curve aside, there is something other than just looks that kept this UI pattern alive all these decades.

How I see it [1], absolute values don't matter audio software, except when working with loudness compliance or some very technical things. What's important is how things sound, and it's generally a bad practice relying on UI metering to dial in sound in most cases. The typical audio work involves fine tuning parameters until things feel right. In UX terms, relative parameter tuning is the most common kind of interaction, and sliders absolutely suck balls at it, in my humble opinion.

Linear sliders actually have more inconsistencies across implementation than knobs, that have converged to more or less the same pattern. E.g. some sliders reset value if you click in the middle of it, at which point all prior tuning is lost - this is super annoying and I hate it. Others operate in relative mode and they're similarly intuitive in regards to which direction they should operate depending on slider orientation (should horizontal slider change its value with up-down movement? should interaction range extend beyond slider length?). Also, such sliders are identical to knobs, essentially, but take more screen space.

So, in a a nutshell, knobs are superior for fine tuning, which is 90% of all audio software interactions.

1. I'm not a professional, but I have clocked in thousands of hours into DAWs and other related software over the years as a hobby, also I played on a few local gigs and made some simple audio software.

The scroll wheel usually works for these as well.

Nailed it. Even if the knob worked like a real knob, it would suck. I'm supposed to drag the cursor around in a circle? What a fussy PITA. And what is the hittable zone for that? The very edge? The center to the edge? Some slop area beyond the edge too?

Just no.