Ayu's vocal range

[waterballoon]

I only know in SEASONS she uses the falsetto in the chorus

"sonna hibi ga atta ne to, waraeru hi ga kuru darou"

She uses her falsetto (or something really similar to it; it's out of her comfortable range, but she still manages to hit, so it's either a falsetto or she's straining which I'll explain later again).

Then in her zomg songs like M and Dearest; the final screeching chorus... it doesn't sound like falsetto... more like she's straining her voice to reach those notes which sounds really uncomfortable.

For her A Song For xx album, where she sounded really screechy and high... I attribute that to improper vocal training... the whole album sounded kinda nasal too; so it's likely she used her nasal voice to sing that album, and not her diaphragm, which she started to use like since Duty, I feel.

Also, in kanariya where she sounded really high... I actually feel like they edited her voice to be that high to create some kind of effect (birds do sing really high; maybe she wanted to be like a canary that's singing)... which could explain why she never performed this live lol.

Finally, all these are my personal opinion, so... don't take them too seriously! ^^