Proceedings of the International Conference on New Interfaces for Musical Expression El-Lamellophone - An Open Framework for Low-cost, DIY, Autonomous Lemellophone Based Hyperinstruments Shawn Trail Duncan MacConnell Leo Jenkins University of Victoria University of Victoria University of Victoria Computer Science Computer Science Electrical Engineering [email protected] [email protected] [email protected] Jeff Snyder George Tzanetakis Peter Driessen Princeton University University of Victoria University of Victoria Music Computer Science Electrical Engineering [email protected] [email protected] [email protected] ABSTRACT playing while allowing the performer to engage various spe- The El-Lamellophone (El-La) is a Lamellophone hyperin- cific sensors with broad or minute arm/hand gestures or strument incorporating electronic sensors and integrated explicitly with the free fingers. The unused surface area of DSP. An embedded Linux micro-computer supplants the the body is ideal for intuitive sensor placement, while direct laptop. A piezo-electric pickup is mounted to the under- audio acquisition is simple and robust via a piezo trans- side of the body of the instrument for direct audio acquisi- ducer. Lamellophones are typically sheerly acoustic folk tion providing a robust signal with little interference. The instruments, however, augmentations, such as ours, equip signal is used for electric sound-reinforcement, creative sig- the instrument for contemporary settings where audio pro- nal processing and audio analysis developed in Puredata cessing and sound reinforcement are commonplace as well (Pd). This signal inputs and outputs the micro-computer as offering experimental, novel sound design and interactive via stereo 1/8th inch phono jacks. Sensors provide ges- multi-media performance practice capabilities. ture recognition affording the performer a broader, more dy- namic range of "musical human-computer interaction"(MHCI) over specific DSP functions. The instrument's metal tines (conventionally used for plucking- traditional lamellophone sound production method) tines have been adapted to in- clude capacitive touch in order to control a synthesizer. Ini- tial investigations have been made into digitally-controlled electromagnetic actuation of the acoustic tines, aiming to allow performer control and sensation via both traditional Lamellophone techniques, as well as extended playing tech- niques that incorporate shared human/computer control of the resulting sound. The goal is to achieve this without com- promising the traditional sound production methods of the acoustic instrument while leveraging inherent performance gestures with embedded continuous controller values essen- tial to MHCI. The result is an intuitive, performer designed, hybrid electro-acoustic instrument, idiomatic computer in- terface, and robotic acoustic instrument in one framework. Keywords NIME, proceedings, LATEX, template Figure 1: El-la: Tines are capacitive touch sensors 1. INTRODUCTION Previous work in lamellophone hyperinstruments can be reviewed in [9]. Our design is meant to be adaptable, eas- Lamellophones have a series of tines that are fixed at one ily replicable [5], and open-source so that any lamellophone end and free on the other. The musical tone is produced by performer could render their own version with little engi- depressing and releasing the free end with the thumb allow- neering background. El-La utilizes relatively easily sourced, ing the tine to freely vibrate. They are ideal instruments low-cost components drawing from Konono No. 10s [3] spirit for augmentation being handheld, compact and ergonomic. of using salvaged electronic components to develop new The instruments design facilitates uninterrupted traditional electro-acoustic instruments, analog signal processing and amplification systems for their neo-traditional lamellophone Permission to make digital or hard copies of all or part of this work for based music. personal or classroom use is granted without fee provided that copies are The instrument in its native state is made from wood not made or distributed for profit or commercial advantage and that copies which is hand carved with an effigy at the top for ornamen- bear this notice and the full citation on the first page. To copy otherwise, to tation. The tines are mounted to the body in the conven- republish, to post on servers or to redistribute to lists, requires prior specific tional method with a bridge. Additionally, small metal rings permission and/or a fee. NIME’14, June 30 – July 03, 2014, Goldsmiths, University of London, UK. have been added to the tines to create a desired sustaining Copyright remains with the author(s). buzz when the tines are plucked. This is typical of many 537 Proceedings of the International Conference on New Interfaces for Musical Expression traditional African instruments [4]- which is interesting that chosen for the resistor in series with the Force Sensitive Re- it is a type of acoustic distortion filter. The body has been sistor (FSR) by connecting the FSR circuit to the gain CV carved out on the inside creating a resonant chamber. The of an analog synthesizer while viewing the output voltage instrument is tuned to a single diatonic scale. Since the on an oscilloscope. This value gave the best compromise instrument is non-western, and therefore doesn't conform between music expressiveness and full-scale reading on the to the tempered chromatic scale, the suggestion of the oc- oscilloscope. Also mounted on the back panel is one XY tave is only relative to each preceding note when ascending resistive analog joystick accessible by the left middle fin- the scale. Meaning, the instrument is tuned by ear and not ger. On the side panel one SoftPot resistive membrane is by mathematically uniformed spaced intervals. The exact mounted. The pushbuttons connect to the digital pins of frequencies of each tine can be reviewed in[9]. the Arduino board, while the rest of the components con- nect to the analog pins. 2. HARDWARE : SENSOR INTERFACE El-La incorporates a capacitive touch sensor controller, a three-axis gyroscope, a force sensitive resistor (FSR), 6 switches, 2 rotary Potentiometers, a membrane slider potentiometer, an xy axis joystick, and LEDs for visual feedback. To fa- cilitate easy sensor acquisition, all sensors interface with an Arduino Nano. The capacitive touch sensor controller interfaces with the Arduino using an I2C interface, while the IMU outputs all sensors processed by its onboard AT- mega328 via a serial stream (UART). All other sensors (but- Figure 3: sensor interface (l) and Beaglebone (r) tons, pots, joystick, and FSR) interface by way of the Ar- duino Nanos analog and digital inputs. The Nano plugs directly into and is powered by the Beaglebone and com- municates via USB. The whole system is modular, easily 2.2.2 Capacitive Touch removable and packs into a case for transport. For this implementation we use 20 AWG wire soldered to the eight (8) tines on the El-Lamellaphone as electrodes. Each wire was then connected to the MPR121 Capacitive Touch Sensor Controller2 from Freescale. This package is capable of controlling twelve (12) electrodes and interfaces via I2C protocol. It also includes a three-level filtering pro- cess to eliminate any noise-induced detection. The max- imum response time is 32 µsec and its output byte con- tains touch/release status for all tines. An advantage of this package is that it allows simultaneous touch detection of the eight tines- which in this case is used for polyphony. 2.2.3 9DOF For the gyroscope implementation we use an InvenSense ITG-3200 three-axis (X (roll), Y (pitch) and Z (yaw)) gy- roscope with I2C interface. This small package (4 × 4 × Figure 2: flow chart of modularity of componants 0:9 mm) digitally ouputs rotational data from any of the three sensed axes at a rate of 20 msec. In the current implementation the gyroscope is built into a 9DOF Razor 2.1 Piezo Inertial Measurement Unit (IMU)3 via I2C protocol. The A contact microphone, mounted on the body of the El- IMU's firmware scales the 16-bit output range of the gyro- Lamellophone, is connected straight to the 1=8" audio jack scope into a [−180:00; 180:00] range for each axis and then of the Beaglebone board to acquire the audio signal. The transmits the rotational data to the host Arduino board signal is then processed in Pure Data. via the serial ports Tx and Rx, at a baudrate of 56700 bps. Figure 4 shows the direction of rotation of each of the 2.2 Arduino and Sensors - HCI sensing axes, in reference to the El Lamellophone. In the The Arduino Nano is a small, complete, and breadboard- future we will use a cheaper platform for prototyping. This friendly board based on the ATmega328 (Arduino Nano 3.0) model was readily available at no cost so we chose to use and works with a Mini-B USB cable 1. it at the time. Lamellophone based gesture sensing using an IMU builds on previous work that was sketched using a 2.2.1 Switches, Pots, FSR, Joystick, Membrane Wiimote [9]. The HCI components of the El-Lamellophone are strate- gically located so that they don't interfere with the per- 2.3 LEDs former's playability of the instrument in the conventional A 10-segment LED bar graph is used to provide state and sense [8]. Six Pushbuttons and two (47k - the value cho- sensor feedback to the EL-lamellophone user. To econo- sen was arbitrary) rotary potentiometers are mounted on mize the wiring footprint and then number of Arduino pins the upper back panel- accessed by the left