A gentleman in the UK by the name of Giles Whittome owns a 'crookless' Wohlrab trumpet, which we photographed and published on p33 of The Brass Instrument Manual, along with many other curiosities Giles owns. Wohlrab was a maker of quality instruments in his day but I can only imagine that the slide-free design was the result of a complete obsession on his part. Suffice to say, it massively increases the complexity of manufacture as the 'missing' tubing is inside the valves. Even worse, it deprives the player of the ability to modify the slide lengths. As a result, it is a classic example of an engineering solution to a problem that was never particularly significant in the first place, unlike the whole series of problems it introduces. To be more specific: unless you are a brass player, you probably won't even notice the difference and if you are, you'll surely find a better-playing instrument for the money. For all that, hats off the Mr Wohlrab for turning such a crazy concept into a playable musical instrument!