I just went through this on my horn... I liked a bit of it, but it needs more intensity. The part from measure 25 to 36 is a bit boring in my opinion, not much is happening, it's polluting the rest of the piece with boredom. In my opinion you need more ....
stuff to balance with this section. It sounds like a great place to modulate upwards a step or two, build some intensity.
I'm normally more comfortable with the high range stuff, so I had a hard time with all the low G's you've written. Even to a better horn player these quick snap to low G and back tend to be sludgy and lethargic, unless you have a great horn player who excels in the low register.
Since I just played it, I had an itch to change a few things... one of them is measure 24.... regardless whether I can play it well or not, I just don't like this measure, it doesn't seem to meld with the rest or provide a smooth transition into the next section. Measure 12, the repeated eight notes in the piano.... I think you should change these repeated eight notes/quavers into Bb's, I think it sounds more interesting that way. Measure 16, due to the building intensity, I've wanted to play a high G every time I've hit this measure. I would suggest in the horn for the second eighth note/quaver to be a high G with an accent like the D. Leading into 17, I felt that the piano needed more attention... I would suggest a stronger dynamic in the piano and possible a pianissimo/pp in the horn, horns are loud, remember?

Pianissimo here in the horn sounds beautiful. Also in 17, I think the right hand should have accents on the downbeats like the left hand, possibly even on the third note of those measures, but not entirely necessary, I think it's 'felt' anyways. I really like measure 36 to 41, especially since it's a nice calm little interlude and the horn just bursts in with the Kall (though I would suggest a loud dynamic leading into 41). In measure 36, I suggest the eighth notes/quavers in the piano be changed to Bb's just like I suggested in measure 12.
Also, every time I play it, it seems like that pickup that the horn has, the eight note followed by two sixteenths, it seems to me it should be tongued, not slurred. Maybe slurred the very first time and any subsequent time at a piano or pianissimo, but at any louder of a dynamic, when I play it I tongue it, so I suggest unslurring all those figures except the very first one. I also feel that the dashes/tenuto markings you have measures 16 and into 19 are unneccesary... possibly slur the whole passage three notes at a time, the two pickups and the downbeats, makes more sense to me.
I'm not very convinced that the ending is all that effective... I didn't like how you went to the F major chord in the final measure, I would have used another C major chord instead. And at measure 44, have the horn hit a high G on the 'and' of '1', right after the first D, after the breath mark, and have the G held and faded out until the end, merging with the C chord that I would put in the last measure.... and a fermata on the last measure I think is needed or would at least be a plausible idea.
I enjoyed this call, or 'Kall', but I think you need to keep up the intensity in it a little better, changing around a few chords/notes (some I mentioned) and changing a few dynamics here and there (again, I mention a couple places). Other than all that, I really liked the sound, feel, and sense of meter in this piece, I like the heavy pounding chords, reminds me of MechWarrior 2 for some reason....
