:Several things 
 :#There was no reason to drop the whole section on "why modulation", since it contains perfectly correct, standard reasons for modulation. 
 :#The section it was replaced with focuses entirely on antenna length; well yes, modulation has an effect on that by allowing us to shift up in frequency, but it's not the principal reason. It should be mentioned, but an approximate calculation of antenna length doesn't really have a lot to do with modulation: that info belongs elsewhere, and the text already mentioned "smaller...antennas". Plus, the example was a bit peculiar: why would we ever try to transmit at 20kHz? 
 :#I didn't understand "Logical Reason" at all. We don't transmit signals at that frequency, but I'm not sure with what they would get superimposed, apart from human speech. It's an odd point to make, and again not directly related to the topic of modulation. (And why is this 'reason' logical?) 
 :#"Redundancy" has nothing to do with modulation. Modulation doesn't introduce or require redundancy. I think you must be thinking of coding, where redundancy is key. Then the text in that section seemed to have nothing to do with redundancy, but did seem to be an unusual statement of the means of modulation — which is already present in clearer, cleaner language right at the top of the article. 
 :#The musical use of modulation belongs at the top of the article, because that's how we do things like that in lots of other pages. 
 :#Modulation seems odd in Category:Electronics and Encodings, since the article doesn't talk, or need to talk about electronics (it would belong in the individual schemes' articles) and modulation isn't an encoding. 
 :#The other categories you added were sensible on closer inspection, and I will reinstate them. The horribly overlapping nature of those category names does reveal the mess that the various parts of the comms categorisation scheme is in. -