A pocket trumpet is a normal b-flat trumpet
, squashed down to a more portable size. The secret is in the arrangement.
If you took a regular trumpet and stretched it out alongside a stretched out pocket trumpet, the tubing would be roughly the same length. The difference is that in a pocket trumpet, the tubing is more tightly wound. Because of the arrangement, pocket trumpets are hard to tune if the player wants a traditional trumpet sound.
A pocket trumpet offers novelty, portability, and a generally low price. However, most other aspects of the instrument are sacrificed. Only in very high end models is the quality of sound produced equal to that of a good normal trumpet. Also, those high-end models tend to be more like a regular trumpet, often having a full size bell
A pocket trumpet cannot really fit in your pocket. I have seen it done only once, and that was when pants with really huge pockets
were popular. The band teacher let a skater kid try and get the whole thing in his side pocket; needless to say, he succeeded. Most pocket trumpets are about 9 inches long, with about a 4-inch bell. They cost around $200 used, maybe $300 or more new.
A pocket trumpet is a really cool thing to have for practice; fun at sporting events, and other times when a regular trumpet is not necessary and the bulk would be prohibitive.
If you wish to buy a pocket trumpet, play several before deciding on one, and also check out used ones. Because of their popularity, used pocket trumpets are easy to come by.