This article discusses the augmentation of acoustic musical instruments, with a focus on trumpet augmentation. Augmented instruments are acoustic instruments onto which sensors have been mounted in order to provide extra sonic control variables. Trumpets make ideal candidates for augmentation because they have spare physical space on which to mount electronics and spare performer “bandwidth” with which to interact with the augmentations. In this article, underlying concepts of augmented instrument design are discussed along with a review and discussion of twelve existing augmented trumpets and five projects related to mouthpiece augmentation. Common aspects to many of these examples are identified, such as the prevalence of idiosyncratic designs, the use of buttons placed at or near the left-hand playing position, and the focus on measuring or mimicking trumpet valves. Three existing approaches to valve sensing are compared, and a novel method for sensing valve position, based on linear variable differential transformers, is introduced. Based on the review and comparison, we created an example augmented trumpet that tests the feasibility of a modular design paradigm. The results of this review of the state-of-the-art and our own research suggests future directions towards a better understanding of augmented trumpet design.