Ahhhh, I'm not missing anything then! Maybe I'll get round to it at some point but I've got a load of stuff to do first.That's a screw that is used to hold a lyre for when you're in marching band. Unless you have a need to put your music on a lyre while marching around you don't need it. It would be nice to have just to make the instrument complete. (mine is missing on my 10M) There are those who say that if you replace the stock one with a massive tungsten screw it will change the tonal quality of your instrument's sound. I just threw that in to stir the pot a little. ;0)
You can even buy replacements online provided the Martin screw threads match a Yamaha. https://www.amazon.com/Yamaha-Saxop...557075624&s=musical-instruments&sr=1-20-spell
But the forum is internationalWhat has that to do with anything? The horn was made in America when we were using all SAE threads.
I liked this answer.That is the volume knob. The one in the front is the gain.