I really like this "Tangible Scores" project by Enrique Tomas, a PhD student at the University of Art and Design of Linz (at the time presumably). It is a tool for making music essentially, featuring a wood board with scores on it in various shapes, such as a scribble, or a series of parallel lines. A program senses the user's touch and gestures across the augmented surface, and translates it to sound. The actual mechanics of the project are very, very complicated (there is a paper explaining the design and concept in more depth).
I love when the human mind sees meaning in abstract patterns(such as a series of lines looking like instrument strings), and art and technology allows us to experience those imaginative thoughts for real(strumming your finger across it actually creates a strumming sound). And I find the combination of tactile, visual, and sonic elements particularly interesting, since you can essentially see and touch the musical forms created from it(because the musical forms were created from these visual and tactile forms to begin with).
What is somewhat off-putting about the project is the contrast between the way it is demonstrated in the Vimeo video and the way it was displayed in a gallery. It invites a very different kind of interaction, where it seems like you would feel more like you're making sounds than making music. Something about the gallery setting, despite being immersive, is rather empty and unwelcoming.