I am just curious if anyone else has done this. I believe that if you can learn where the slots are on your leadpipe and learn to play them, adding the horn just makes them sound like a trumpet. In college, I would remove my main tuning slide and practice finding the slots of my leadpipe. This made me very aware of every little thing i was doing embouchure-wise. It also helped me focus on the smaller adjustments needed when going up. When I would practice range with the whole horn, mentally it seemed much harder. (Yes, I know that the blow is different. I am not saying I played Arbans on the leadpipe. Just worked at getting it to sound the slots that were there).
More recently, to really tighten up my aperature, I have spent some time playing the horn without the mouthpiece, just buzzing directly into the leadpipe opening. This has been helpful in getting the lip muscles to contract and shrink the aperature. It also forces me to use a combination of lip control plus air control, because pressure cannot be relied on (or you would cut your lip). Of course, it does not sound "trumpety," but I find I can play from pedal C up to F above double C by doing this exercise without the mouthpiece. (I only spend maybe 5 minutes max doing this before practicing, typically just doing scales or arps).
Just wondering if others have done this and benefitted.