Okay. There's two growling techniques that are commonly used.
First one is almost like gargling or gargling with your tonsils whilst play a note. And that is kind of like. Doing that into the saxophone. Like that.
The other commonly used way of growling is to sing a note also into the horn. I'm not sure if the note matters but the process of having another note being sung into the horn will give the same effect. Check it out.
So that's commonly used in rhythm and blues music. And then I'm sure in a lot of your favorite pop cellars out there.
The growling technique on the alto saxophone.