Oh! Nice

It isn't exactly what I was referring to as soundical illusion, but its a clever trick.
The idea of a soundical illusion is presenting something, where you can find something else if you know what to look for, or present something that sounds theoretically impossible.
I had some idea's too.
The infinite toneladder has been mentioned before as conversion of the infinite staircase.
Next its also possible to make notes/noise and put it in such way, that if you play it while using a spectral analysis, you'll see an image pop up. Like a smily or a face or whatever.
Another idea I had was to make a very static 4/4 beat, and use a special techique to make it transform into a 3/4 beat, which sounds technically impossible becaues you either need a fill or fade technique, which could make the beats sound overlap getting a mess. But using clever tricks you can layer them over eachother and carefully apply tweaks to make it go from one to the other.
Another idea I had was by finding a vocal sample, and use somekind of technique to seperate it in different layers that would not make you recognise that they're vocals. Then you make a song with each of them playing seperatelly, and then at some point, make them slowly blend togehter so you suddenly hear the voice that initially was recorded.
I had more ideas but I can't think of them at this moment.
Do you guys have more ideas? maybe even thinking of them now after reading mine?