Thought about DJ real-time performances

[Krakatau]

I just had a glance on twitch of a performance from shelter records of NYC

I'm wondering on how these cybershows are builted up, how Dj machines are selecting and bringing together compatible musical themes, harmonically and rhythmically, where are the sound sources coming from, etc, etc...

To say that its a brand new world for me

[osiris]

I know about Traktor and have used it and it's good.
Song Key and BPM I use the website Tunebat.