HITar

The HITar augmented guitar was created by Andrea Martelloni, Andrew McPherson, and Mathieu Barthet at Queen Mary University of London. It takes inspiration from the practice of percussive fingerstyle acoustic guitar, which involves layered arrangements, altered tunings, and percussive techniques on the guitar's body to enable musicians to act as a "one-man band". The HITar builds upon percussive fingerstyle's tradition and aesthetics, and reinvents the way the player can interact with the guitar's body by expanding its timbral control.
The HITar technology works with a regular acoustic guitar with five piezo sensors added underneath the areas of the body most used in percussive technique. An Artificial Intelligence engine processes the signal of the piezo sensors in real time, and recognises which part of the hand is used for each hit. This enables to describe the technique used by the player, for example, heel, or fingers. Our AI engine can also "morph" organically from one category to another as the musician gradually moves from one part of the hand to another.
We built a HITar prototype around the MetaSynth physics-based synthesis model by the CNRS-AMU PRISM laboratory (France), by driving the model from the piezo sensor's audio and controlling its parameters with our AI engine. In our demo video we present another HITar prototype where the AI engine outputs MIDI messages enabling to control sample-based virtual instruments, such as Spitfire Audio plugins, and other MIDI devices.

The HITar was designed to bridge the gap between the physical and the digital using AI. We wanted to describe each individual percussive hit through a rich and multi-dimensional representation, capturing more than just hit category (e.g. type of sample to be reproduced) and velocity (how loud it's supposed to be). Therefore, we tasked the AI with finding out what makes each body hit different from all the other hits of its class.
This innovation opens up a totally new range of possibilities to percussive guitarists, who can control a digital percussion instrument with timbres not limited to those of a wooden body. Still, the richness of the control yielded by the HITar offers an intimacy and an immediacy not possible with buttons or conventional MIDI control surfaces. Since the strings are sensed by our AI engine too, string hits and slaps also become an organic part of the new generated sounds.
The AI technology behind the HITar is not limited to guitar drumming. If deployed into electronic percussion, the algorithm can offer more richness than conventional sample-triggering electronic percussion, while still providing the flexibility of MIDI compatibility that is lacking in other digital percussions with proprietary synthesis engines. This technology has the potential to develop into the solution for expressive digital percussion similarly to expressive keyboard controllers like the Continuum or the Seaboard.

The most immediate use of the HITar is to expand the vocabulary of sounds of percussive guitar, especially to support techniques and sounds that are idiomatic of other percussions but cannot be done on the guitar. For example, with the HITar, the heel of the hand can be used to mute a digital drum, whereas finger hits can be used for resonant hits, introducing the same muting techniques of skin membrane drums.
HITar players can appreciate the fact that their guitar body can sound nothing like a guitar's body. With the MetaSynth engine, we demonstrated that different hand positions can be associated to nuanced synthesis parameters, e.g. the tension of a virtual string or the material of any other virtual surface. Sample libraries can also be used to expand the sound palette to drums, cymbals, world percussion etc., all the way to cinematic soundscapes. The guitar then becomes a compositional tool even beyond the "one man band", opening up uses such as film scoring. We invite you to watch the video included in this submission showcasing all these options.