Two thing I can think of.
- As humans, our tongue is most involved in talking and eating -- (Italians excel at both!) and so it is "normal" for the jaw and throat to move (like in swallowing, for example. Away from the horn, look in a mirror and practice saying "tititititititit" without any visible movement.
- With the horn, instead of thinking "attack," think "release." Rather than concentrate on the forward motion of the tongue, concentrate on the tongue motion as it comes back.
There are tons of different approaches -- try these, and if they help, great, if not, listen to our other friends here at TM.
Have fun!