"an unnatural way"
On the contrary Dick
We all have a wide ranges of tones - we use most of them in speech but very few in singing, for various reasons
Bert's 'grin' was a lazy-man's method of producing an unused tone away from his habitual speaking tone in order to sing songs requiring a different effect - there's nothing unnatural about it
Some traditions use other methods - physical intervention, by pressure on the throat or holding the head in a different position
The most extreme form of intervention was used by the 'Castrati' until it became illegal - cutting a young lads balls off
I; happy to go into this deeper but not now
Jim