Miles was not a well-rounded player from all I've heard of his playing. He never played in a symphony orchestra section, he never played in a brass quintet/quartet, I doubt whether after high school he played in a concert band, he wasn't a first-call studio trumpet player. He was a superb jazz trumpet player who did what he did better than anybody else, which is why he's a giant in the jazz world. But that doesn't make him a well-rounded player. Was his head buried in the sand? Sure, regarding classical trumpet playing and other aspects of trumpet playing other than what he chose to concentrate on. But how many of us are able to build trumpet-playing lives like Miles did? For most of us, if we want to play the trumpet and earn some money at it, we need to be able to do many different things with our horns, from playing in a symphony orchestra to playing in a pit orchestra for a broadway-style show to playing in a rock/blues band to playing in a small jazz combo to playing in a big band. And all of those different styles require a much larger range of playing capabilities and knowledge than many people who simply concentrate on a single playing style and do it extremely well. Wayne Bergeron is an example of a trumpet player who is pretty well-rounded, as is Wynton Marsalis. Turtle is absolutely right that nobody has to do anything they don't want to do in music, but eliminating certain aspects of trumpet playing reduces the well-rounded-ness of a person. Not being well-rounded isn't a good thing or a bad thing, but it's a luxury that very few trumpet players I know of can afford to do. If your trumpet playing is purely a hobby and you don't expect to get any paying gigs, then play and practice only that which makes you happy. But it won't make you well-rounded, if that's your intent. The only thing wrong with trying to play like Miles is that he's already done it and nobody ever plays like Miles, really. They simply play like copycats. Same with people who try to specialize in Maynard charts. Play like *you* and find where your trumpet voice is and work on that. For me, I really enjoy having many trumpet voices. Your mileage may vary.