My jaw seized up rather suddenly and was getting worse by the day. The tension in the jaw joint was becoming severe -- uncomfortable and painful, and I could not open my mouth without a miserable jarring pop. Because my godmother has been through a years-long full mouth reconstruction, I asked her what I could do. She told me that a tibetan singing bowl helped her a lot. I didn't have access to one, but a couple days later it occured to me to just hum. So I did, for about ten minutes on my drive home, and then I went to bed. The next morning my jaw was most of the way better -- I barely noticed the pop of the dislocation, once I had warmed up the joint. While humming that first time, while the tension was severe, my eardrum buzzed/rattled like a broken speaker! The next day there was no more buzzing when I hummed. I still need to accomplish a complete cure, as I my jaw is still dislocated since the onset of this bout of tension; however, that will probably require a wisdom tooth extraction. Now it clunks when I open my mouth, but does not cause me any discomfort.
When I was in college years ago, I took a class on the Linklater Voice method, which was recommended for actors and public speakers. I remember being told that one of the exercises we used to warm up at the beginning of class was excellent at reducing or eliminating TMJ. This particular warm-up exercise consisted of grabbing a good hold on your chin between your thumb and pointing finger and vibrating it (shaking it very quickly with tiny movements) while making an "AHHHHH" sound. Then you'd continue with the vibration and make a very deep sighing noise going up and down the scale (picture a sound wave curve). You might want to do this in a sound proof room because people may wonder what the heck you are up to -- very silly sounds!
I have used the technique successfully over the years to treat my TMJ when it popped up. I spend 5-10 minuts making sounds and vibrating my jaw. I also move my jaw from side to side while making that AHhhh sound.
Magnesium is a potent stress reducer, so you might consider taking that too.
P.S. I haven't checked, but maybe there are some videos on YouTube on the Linklater voice method to give you an idea.
P.P.S Babies sometimes make a very similar sound to the vibration I described above!