This question can apply to all those who classify themselves as DJs. Used the David Guetta example as it was recent.
In the closing ceremony David Guetta came on to the ground where an elaborate set of decks was in place. Music started playing and David started moving knobs around with both hands flicking them in some random fashion contorting his hands as he moved from one knob to another. The impression given from all this mechanical actioning was that it was very crucial to time his knob moving skills accurately.
To my ear it sounded like some sort of dance music and any precise changes he was making did not alter what would have come out of the speakers anyway. It was all dance music type thing very samey.
So what do they do when they contort their knobs in that fashion. Is it ultimately important.
However, it’s important to note there’s a huge difference between a DJ in a club mixing other artists’ pre-recorded music together and a DJ mixing disparate samples into a relatively original composition. My previous comment is in reference to the latter, which I assume is what David Guetta does (I’m not familiar with the name).
I am not familiar with that particular artist or performance, but in general what DJ’s do is to take a bunch of part of separate songs and weave them together to form a more danceable song. In order to do this without being jarring the number of beats per minute must stay approximately the same between transitions. So when a transition is going to occur the DJ is speeding up or slowing down both songs so that they match and then slowing or speeding them up after to achieve a desired affect. These things have to be done at precise times to keep the transitions from being jarring. This is somehow accomplished through dials and knobs and was probably what Guetta was doing or pretending to be doing.
Since I haven’t seen the specific event that the OP is talking about, I’ll assume he’s playing pre-recorded music (of his own or that of other producers) and he could be doing any number of things to change how that music sounds, such as dialing in various effects (delays, reverbs, EQ and filters, etc.) that have somewhat dramatic outcomes on the music program. . . modern DJ mixers have lots of routing options and he can also be layering various tracks on top of one another to create a more interesting song. . . but this is David Guetta and it’s probably safe to assume he’s just reacting to an entirely prerecorded set. . . lip syncing is what we called it back in the day. . .
From the bits and pieces I saw and heard from that, a lot of the knob twirling was related to filters. I mean, the piece may or may not be prerecorded, but the movements he’s doing with the knobs do go along with what is happening in the music.
