Silver tarnish removal treatment generally produces pretty spectacular results.  There is a great deal of difference, between horns, however, in their repair and use history.  Ultimately, the state of the horn itself largely determines the result of silver cleaning.  Tarnish treatment and cosmetic cleaning will do away with years of corrosion, and get the dirt off, but it will not of course put metal back on the horn, or remove scratches from the horn's surface.

The photos below are of a recent tarnish removal job, on a horn that William & I cleaned up recently, for overhaul & sale.  This "Chu" alto was an unusually well-preserved example, beneath the dirt & tarnish, & the final result reflects this as much as our work.

About the pics:  the contrast/brightness settings are different in the pics because they were taken and edited on different days, and in some of the "before" pics the exposures were with flash (those with the purplish cast to the backdrop are the flash-lit photos).  When I find the time, I'll try and take more pics, of another job, with some more consistent photos.  For now these pics do give a realistic illustration of "before" & "after" results, with a horn in exceptionally good condition, & with medium to medium-heavy tarnish.