Disclaimer: I have never taken proper singing classes so my vocabulary may be incorrect, I hope you understand what I mean.
Thanks to my quite late voice change (when I was ~15) I have have developed a taste for high-pitched singing.
Before the voice change, my range was about A3-F6~A6 depending on training.
Later I kind of grew into a baritone voice (not exactly sure about that) which went from G2-G4, and a falsetto/whistle that was quite airy and could still reach A3-F#6.
At first I wasn't able to get a mixed voice, so I could either sing ~soprano or baritone (not very practical for most classical rock). With some practice I was able to get to this mixed voice to have a stronger upper range from G4 to B5 (sounds more Rob Halford than Axl Rose unfortunately, but working on it).
After screaming a bit too much during a party and getting sick two years ago (was 20 at the time), I lost my voice for a few days. When I recovered, I could not use the whistle/falsetto register with the same technique I had always used, it either 'fell back' to mixed chest up to B5, or simply made no sound as if the voice were broken. With time, I was able to use the falsetto voice again if I sung softly around the 4th octave, but to this day I'm unable to use this voice for singing very high notes.
Is there anything I can do to recover whistle register? I'd be elated if I could sing the end of Aerosmith's Crazy again, would that be possible?