Any music teacher will tell you. It's hard to sing with a petted lip.
So the Tartan Army might find it rather difficult to give their usual rendition of 'Doe, a Deer' the full Monty when they next congregate to chorus hymns of praise for our national team.
It seems that some have not taken well to Great Uncle Walter's defection back to his true love, although it didn't stun me. The elastic band just won't break, will it?
He's a huge loss to the national cause.
You have to think where Scotland stood in the great scheme of things just 25 months ago, when he offered salvation in the wake of the great Berti Vogts depression.
Hands up anyone who fancies this man for the Hampden hotseat
Our Fifa listing read like a heart rate, except you could barely feel the pulse of our national side.
In those two years, we have soared 60 places while Great Uncle Walter's golf handicap has plummeted.
That's the bit I just don't get. Why at his time of life he would throw himself back into the insanity of an Old Firm job while all was tranquil at national level. I'll wager Ethel, his dear wife, is horrified at the prospect.
Mind you, her housekeeping allowance might have a little lift. My guess is that his wages have just trebled.
But it's his life to live and I suggest bitter and twisted Scotland fans who are more intent on branding him a traitor rather than acknowledging what the bloke has actually done for this little nation take a reality check.
Sir David Murray said he was the only choice for the job. Maybe so, but at least that was one more outstanding candidate than the SFA have.
David Taylor and his board did the right thing, a show of defiance and a dig at Murray. But, once the Rangers chairman dialled Walter's number, he would have escaped from Guantanemo Bay, never mind Hampden.
Even Ally McCoist found it irresistible, promising to totally forsake his career in broadcasting, which - at the last count - clears the way for 15 vacancies in television.
But it may be more than McCoist who is out the picture now.
Scotland are suddenly in danger of losing sight of the 2008 dream, the one that had the Tartan Army cascading over the Alps into Switzerland and Austria like the Von Trapp family in kilts.
In fact, Julie Andrews seems to have as much chance as the next man of getting the manager's job.
Tommy Burns must be first port of call. Walter's trusted assistant, bloodied veteran of the Vogts campaign and trusted by the players.
Beyond that, Gary McAllister - limited on coaching experience - Craig Levein, who once went to war with the SFA, or Jim Jefferies? There isn't exactly an orderly queue of legitimate candidates.
But I'll throw one at you. Graeme Souness once created a job for Walter Smith. Maybe it's time to return the compliment.
A former captain of his country, hardly short on managerial experience. Oh yes, and the biggest plus of all for the SFA, he's available at no cost.
Not the worst idea I've ever had then.