I'm not sure there is a specific secret as such. There are probably several forms of neurologial degenerative diseases and disorders afflicting the central nervous system that could motivate the patient to get into something like that.
No idea what you'd need the DX100 for, but I wouldn't be surprised if there was a second sampler involved to save multitracking.
Pianos have a bit of a Korg flavor to it, typical bright plastic 90s stuff.
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Typical late '90s stuff, you can also easily recognize the Korg M1 style organ and piano.. just get a Roland JV module with Dance and Techno (or even House) exp. boards and you're set with all those sounds. The question is, do you really want to make this type of Aqua-influenced music?
Listening to this one track, which reminds me of Barbie Girl, I'd say this genre and bubble gum music in particular is characterised by a few things:
1. Simple chord progressions of obvious tension and release I-V-I or I-IV-V-I come to mind and maybe I-V7.
2. Basic 4/4 beat with a small dose of polyrythm via the hats or perc.
3. Simple sounds based on synth primary colours (square, sine, saw)
4. Simple baselines that bounce
5. A strong melodic verse with an chorus that will drill right into your skull.
6. Vocals sung by a 19 year old (or younger) with a white guy pseudo wrapping behind her.
You could recreate that sound with the free software synths that come with just about any DAW nowadays. That is not up to current standards. In fact, it wasn't even up to standards when it was made. That is a crappy recording and a worse song. But if you like it then I salute you. You will probably make a hit song someday.