This article examines users’ relationships to mobile devices, their surroundings, and music by concentrating on three interconnected aspects of some recent sound/music apps for the iPhone: 1) the way they suggest a form of musical participation that challenges the separation of listening and performance; 2) how they expand on musical performance gestures to involve larger-scale movements such as walking; and 3) how this occurs in public space. After briefly contextualizing the apps by looking at the player piano, which also blurs the line between playback and performance through gesture, I move on to consider the promotional discourse around the apps, particularly ideas of immersion and personalization. I argue the actual functioning of the apps potentially challenges these ideas as well as the notion of the auditory bubble that has been attributed to mobile music devices. I draw attention to the multidimensionality of gestures involved in the use of mobile devices and how gestures are interconnected with digital, physical, public, and private spaces.