Manually interrupt generation mid-stream

Hi -
Some guy showed me a way to stop generate and play mid stream-I knows its not an official option, but it was an effective work around--I just can't remember what it is? Anyone?
USING BIAB 2015 MAC

I'm running 2016 here, but the "esc" key in the upper left works for me.

Hopefully this helps.

- Jay

Thats it! Thanks!