The ng-sound

Hi everbody,
In german, english and the scandinavian languages "ng" is normaly pronounced nasally with the tongue in the g- or k-position. Now a proffessional language-coach tell me that in certain cases to create a more distintive sound, it is possible to pronounce the g, that is singing-g with the g at the end pronounced g, or long-g in the same way. I think this is wrong in all cases.
What do you say?

I know some people who pronounce the ng as more than just a nasal sound. For example, they'd pronounce singing as "siŋ-giŋg."