You need to distinguish between DJ’s and “producers”. Dj’s play other peoples music, producers play their own.
Ironically producers tend to do the least during live performances. I know one major live psytrance act from the 2000’s was quoted privately as saying “I get paid 5000 pounds and flown to a festival to bring my laptop, press the space bar to start the set and then twiddle my mixer knobs to make it look like I am doing something”.
Dj’s do more live than original acts believe it or not.
Nit: The Disco Biscuits are a pretty fantastic trancyish jam band. They’re name refers back to a slang term for quaaludes (remember them?). It’s not dispositive, but never heard anyone refer to X as a disco biscuit. YMMV. Test before you take.
To be honest I think people are right to be disdainful of what a DJ does live. If someone is playing someone else’s music, yes the beat-matching does take skill to seamlessly move from one track to another no doubt, but hardly great artistry.
As for the ‘DJs’ that are essentially playing music they’ve created quite often they will do some element of what they might’ve had to do when creating the music such as playing a riff on a keyboard or mixing or selecting what certain tracks are playing, but in many ways they might as just “press space” on their laptop.
For me the greatest thing about electronic music is that you can do things you might not be able to simply replicate in real-time, so often in “live performances” of such music, performers are at best limited to doing only a very small aspect in real-time.
Armin van Buuren explains how he syncs the video and sound here.
On this side of the Atlantic, it’s not common for anyone to use X, when they mean E. Disco biscuits is just a jocular euphemism. Appropriate smilies: 
and later :eek:
Sure but the point is that there’s a huge range of correct answers to ‘What’s the DJ doing?’
Take this hilarious live rendition of Thrift Shop by Flula:
[spoiler]https://www.youtube.com/watch?v=QWUPCmDRIO8[/spoiler]Explicit lyrics!
You can see him build the song piece by piece. When he has the pieces ready, he mixes them in and out. The voice sampling at the end is a bit of a weak point but you can see what’s possible in realtime.
Of course, most DJs (and I don’t use the term Producer when live, it is DJ) aren’t singing and making mouth beats, they have a bunch of samples ready to go on the laptop. In the olden days, they would bring samplers, sequencers, drum machines, sound modules (ie Roland x0x), synthesizers, effects processors, mixers, EQs, etc. It was a table full of blinking lights. Here’s a decent demonstration.
Later, there were ‘groovebox’ machines which combined a lot of these tools as shown here. The had more canned sounds and beats built in and were designed and manufactured for EDM.
As with so many other things, computers have largely replaced these discrete instruments. And like so many other things again, computers have given people the ability to simply press Play and get something coherent out. But a talented DJ will still load the laptop with carefully curated song pieces to put together a great show.
So it really is just a matter of laying down a beat and mixing in other parts. Just as an old master made a sculpture by scratching marble or brushing paint, the art is in the vision, technique and skills.
Yeah, that’s a whole other kettle of fish, and very impressive. See also Walk off the Earth’s Loop videos. (no seriously, go see them, very impressive…
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But that’s emphatically not what this guy was doing…
This thread seems to be confusing and conflating “DJs” (who play other people’s records and mix them together) and electronic music acts who create their own music. The latter category are, in my experience, more likely to just “turn up and hit play”, but they have done the work in creating the music in the first place. The former category will (usually) select records on the fly and mix them together live.
This is the important point, and unfortunately one that Deadmau5 ignores as well. Why turn it into a case of “my way of making and playing music is better than yours?” There are different skills involved, and being good at one doesn’t always translate to the other.
I saw hundreds of DJs in the 90s before there was the option to “just press play”, and in addition to the technical challenge of synching the tempo and beats, they were figuring out what songs flowed together and would take the crowd in a certain direction. The best DJs read the crowd: a lot of people on the dance floor staring at the lights? Drop a more trippy track. Sweaty people pogo-ing madly? Throw down the jackhammer beats. People looking a little too tweaky? Bring down the energy a little.
I also saw the Chemical Brothers back in the day - great producers, but boring as hell live. I recently saw Girl Talk - he’s a producer/mashup artist. The skill that goes into mixing 4-5 songs together and have it all flow and sound good is incomprehensible to me. In a live show, his involvement with the music is really no more than hitting the space bar to start it. But it was still a great show. He’s getting people on stage to dance with him, jumping on his table to get the crowd going, and running through the crowd.
Chemical Brothers boring live? They’ve never let me down.
Maybe it was a bad batch of disco biscuits.
Back in my day, the DJ was the (sometimes unofficial/separately credited) member of a rap group who warmed up the crowd, played the backing tracks for the concert, and sometimes did solos, scratch performances, etc. Generally he (sometimes she) performed scratches on the recordings and produced (some DJs served as the producer side of a rapper/producer duo/group but many DJs are not producers. In fact many rappers are the main producer for a group). Sometimes the DJ would be the opening act and/or also DJ for other acts on a bill. Actually, they still do. I am a fan of several current rap duos/groups who have touring DJs and DJs on their records. A lot of these guys do club gigs as well, though not to the extent that EDM stars do.
In general, if you are talking strictly about DJs that perform solo gigs, I think there are at least 3 distinct kinds, if not more. You have some that just “push play.” Some create their own sounds. Others play records but perform turntable skills.