 Although instead of the full range of keys, Vienna horn players usually use an F crook and it is looked down upon to use others, though switching to an A or B crook for higher pitched music does happen on occasion.Vienna horns are often used with funnel shaped mouthpieces similar to those used on the natural horn, with very little (if any) backbore and a very thin rim.The Viennese horn requires very specialized technique and can be quite challenging to play, even for accomplished players of modern horns.