I prefer the traditional ones that have little bits of tin can crimped around the keys so they sound like Esquivel's Buzzimbra, or the guitar on Rumble played through the speaker with holes poked in it.
This is the sort of eerie sound that would be emanating from a previously unseen door at the end of a dark hallways, a wispy blue light fogging forth through the keyhole.
It would play at the start of a Japanese RPG Summon spell, the camera rotating slowly around your character's face, before it suddenly changes into an uptempo Trance-Remix, as Bahamut comes out of the sky, and the fourteen year-old heroine does a magical J-pop dance in a laser-lit cloud of wispy blue fog.