"My vocal range changes if I sing louder (I raised this in a thread last year) - and I have to sing louder to reach higher notes, and then I can't sing low notes at such high volume."

This means that you cannot be using 'correct' vocal techniques - I can't help you at a distance - you should go see a proper voice trainer and explain your problem.



"I find alcohol helps - it may not actually improve your range but it makes you think it has. "

A LITTLE alcohol WILL relax your throat - too much relaxes your brain, and then you don't care - but those around you do.... :-)



"and I have to sing louder to reach higher notes"

You only THINK you do, so you are 'thinking yourself' into stress and 'pushing your vocal formation techniques' - you are in real danger of vocal damage. Perhaps you are not warming up properly IN BOTH SITUATIONS, so that your muscles are not relaxed equally in the differing situations. Less relaxation is likely to 'push your range higher'.



"then I can't sing low notes at such high volume."

Demonstration of you (unconciously) changing your vocal formation technique - you really should seek proper professional help - a bunch of vague disembodied virtual ignoramuses is unlikely to be able to physically observe you and assist you to change your bad habits! :-)