## 4. Actively Augmenting Mobile Devices
### Active Augmentation Framework
### Examples and Evaluation: CCRMA Mobile Synth Summer Workshop

The framework presented in Section 4.1 was evaluated within a two weeks workshop at CCRMA at the end of June 2017 ([[https://ccrma.stanford.edu/~rmichon/mobileSynth](https://ccrma.stanford.edu/~rmichon/mobileSynth)]([https://ccrma.stanford.edu/~rmichon/mobileSynth](https://ccrma.stanford.edu/~rmichon/mobileSynth)): this webpage contains more details about the different instruments presented in the following subsections.). It was done in continuity with the Faust _Workshop_ taught the previous years ([[https://ccrma.stanford.edu/~rmichon/faustWorkshops/2016/](https://ccrma.stanford.edu/~rmichon/faustWorkshops/2016/)]([https://ccrma.stanford.edu/~rmichon/faustWorkshops/2016/](https://ccrma.stanford.edu/~rmichon/faustWorkshops/2016/))) and the _Composed Instrument Workshop_ presented in Section 3.4. During the first week (_Mobile App Development for Sound Synthesis and Processing in Faust_), participants learned how to use Faust through faust2 smartkeyb and made a wide range of musical apps. During the second week (_3D Printing and Musical Interface Design for Smart-phone Augmentation_), they designed various passive (see Section 3) and active augmentations using the framework presented in Section 4.1. They were encouraged to first use elements available on the device (e.g., built-in sensors, touchscreen, etc.) and then think about what was missing to their instrument to make it more expressive and controllable. This section presents selected works from students of the workshop. #### 4.2.1. Bouncy-Phone

[PERSON] designed _Bouncy-Phone_, an instrument where a 3D printed spring is \"sandwiched\" between an iPhone and an acrylic plate hosting a set of photo-resistors (see Figure 10). The interface on the touchscreen implements two parallel piano keyboards controlling the pitch of a monophonic synthesizer. The instrument is played by blowing onto the built-in microphone, in a similar way than Ocarina. The \(x\) axis of the accelerometer is mapped to the frequency of a lowpass filter applied to the generated sound. The spring is used to better control the position of the device in space in order to finely tune the frequency of the filter. The shades created by the two hands of the performer between the phone and the acrylic plate are used to control the parameters of various audio effects. #### 4.2.2. Something Else

[PERSON] designed _Something Else_, an instrument running a set of virtual strings based on physical models from the Faust Physical Modeling Library (see Section 5.2). The touchscreen of an iPhone can be used to trigger sound excitations of different pitches. A set of three photoresistors were placed in 3D printed cavities (see Figure 10) that can be covered by the fingers of the performer to progressively block the light, allowing for a precise control of the parameters associated to them. These sensors were mapped to the parameters of a set of audio effects applied to the sounds generated by the string physical models. The instrument is meant to be held as a trumpet with three fingers on top of it (one per photoresistor) and fingers from the other hand on the side, on the touchscreen. #### 4.2.3. Mobile Hang

Mobile Hang is an instrument based on an iPhone designed by [PERSON]. A 3D printed prosthetic is mounted on the back of the mobile device (see Figure 10). It hosts a Teensy board as well as a set of force sensitive resistors that can be used to trigger a wide range of percussion sounds based on modal physical models of the Faust Physical Modeling Library (see Section 5.2) with different velocities. A large hole placed in the back of the tapping surface allows for the performer to hold the instrument with the thumb of his right hand. The left hand is then free to interact with the different \((x,y)\) controllers on the touchscreen controlling the parameters of various effects applied to the generated sounds. _Mobile Hang_ also takes advantage of the built-in accelerometer of the device to control additional parameters.