I don't think the author was referring to transposition there. I think that was about leaving the notes on the staff the same but just changing the key signatur

I don't think the author was referring to transposition there. I think that was about leaving the notes on the staff the same but just changing the key signature. This is done sometimes as a novelty, and the best example is changing something from a major key to a minor key or vice versa. The article has a link to a recording of Für Elise in a major key [1], and there are many similar renditions of other pieces around. You could in principle do this with any of the seven modes, not just major and minor. As for notes outside the scale, it seems like these key-signature-changing compositions typically keep them the same (like the D# in Für Elise). [1] https://www.youtube.com/watch?v=Y-rZD2AsHbI https://www.youtube.com/watch?v=Y-rZD2AsHbI