Our long dead friend, Mary Garden, talks about the coup de glotte, or 'shock of the glottis'. It's a term used in the theory of singing technique to describe a particular method of emitting or opening a note by an abrupt physical mechanism of the glottis (the space between the vocal folds).

It's a technique I used to sing with that ultimately got me into a lot of vocal trouble.

I'm with Mary on this one... avoid it. 

I'm really enjoying the wisdom of these great singers from the golden age of singing!