MIDI is only half the battle. To make the MIDI "sing" like the original:
Layering: The lead sound is often recreated using synths like u-he Diva. Producers often layer a "pluck" for the transient and a "saw lead" for the sustain to get that thick, evolving sound.
The song's piano riff, which serves as the foundation of the track, was created using a MIDI keyboard. Prydz used a combination of virtual instruments and software synthesizers to craft the distinctive sound, which features a blend of acoustic and digital elements. The use of MIDI allowed Prydz to experiment with different melodic ideas and chord progressions, ultimately settling on a arrangement that has become one of the most recognizable in electronic music.