Countless modern pop songs are full of sounds that aren't made by acoustic instruments; the sound is pure synthetic. You're listening to electricity manipulated by a machine.
The machine of course is the synthesizer, and it's been one of the most crucial building blocks of contemporary music. And yet, how many of us know how a synth works? How do a bunch of wonky tones coming out of a box covered in knobs and buttons translate to the memorable sounds of disco, or synthpop, or house or electro?