Isobel dear I wouldn't laugh at you!
Finally found the email so here I quote neil.clarinet
"As far as technique goes tone is in diaphram support
and the embouchoure, particularly the lower lip. This
can only be improved with practise, and it is knowing
how much to get it right. It's like beibg in the gym
and doing enough, but not to the point where you faint
or pull a muscle. During term I practised 2 hours a
day or more. I now do much less and "surprisingly",
my tone has suffered.
You MUST feel air is coming from the diaphram not from
the chest or throat, nor should either those be tense
in any way. I still get that wrong and my tone
suffers."