The base of the waveform consists of sinewaves and peekwaves. There is very complex chord progression at work with 30+ voices spanning over several octaves.
I used the free Tone2 Firebird Synthesizer to recreate the sound. 2 Oscillators are at work. Base are two simple sinewaves, one at base, and one transformed by an octave, both mono & no effects. The second layer is a Peekwave transformed up by two octaves. Half of the peekwave is mono and without effects, the other half has some fatness, analog dirt & ensemble effects to add some Stereo depth to the sound. After filtering, the result underwent some equalizing and a special Spatial effect Plug-In.
It sounds incomplete in my opinion but I didn't want to make it overly complex and I have only used Plugins that are freeware. You should be able to recreate this file and work from there. You can read all settings from the video. Here is the final product:
It sounds clearly different from the original but the chords are correct. Just replace the Peekwave with your own Piano Synth.
I forgot to show the chords in the video. Unfortunately I couldn't get more than 12 voices at the same time with my Keyboard Plug-In: