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MICROPHONE-BASED ELECTRONIC WIND INSTRUMENT BY FEATURE EXTRACTION FROM BREATH SIGNALS Francesco Bigoni Pelle Juul Christensen Rasmus Eklund Aalborg University – Copenhagen Aalborg University – Copenhagen Aalborg University – Copenhagen [email protected] [email protected] [email protected] Javier Molina Garcia Cumhur Erkut Aalborg University – Copenhagen Aalborg University – Copenhagen [email protected] [email protected] ABSTRACT of acoustic wind instruments to abstract synthesizers. Although the interfaces for electronic wind instruments An electronic wind instrument is an analog or digital went through many years of development and refinement, electronic instrument actuated by blowing onto an they are still disconnected from their acoustic counterparts electronic sensor. Through the history of electronic wind when it comes to sound production techniques. The instruments, the refinement of the physical interfaces has development of a ”good” saxophone sound requires a large not been followed by major innovations regarding breath degree of control over embouchure, reed pressure, air flow and embouchure detection: the industry is still largely and vocal tract configuration; extended techniques such as relying on pressure sensors for measuring air flow. We growling (singing into the horn while blowing), flutter- argue that many sound production techniques for acoustic tonguing (vibrating the false vocal folds while blowing) wind instruments depend on breath quality in addition and multiphonics (playing several tones at the same time) to breath quantity, and that most of the commercially require an even higher degree of awareness regarding the available electronic options do not account for this. A position of the articulators in the vocal tract. However, series of breath signal measurements indicated that an most electronic wind instruments focus on the mere electret microphone flush-mounted in a plastic tube is detection of the airflow by employing a pressure sensor a suitable sensor for feature extraction of the player’s inside the mouthpiece, adding modulation capabilities (e.g. breath. Therefore, we propose the implementation of an vibrato and pitch bend) by a supplementary bite pressure electronic wind instrument, which captures the envelope sensor. It has been shown that the vocal tract configuration and frequency content of the breath and detects whether of the player has an influence on timbre which goes well the signal is voiced or unvoiced. These features are beyond capturing bite pressure and air flow [1], suggesting mapped to the parameters of an FM synthesizer, with an that several modes of sonic interaction through breath are external MIDI keyboard providing pitch control. A simple still largely unexplored. evaluation shows that the proposed implementation is able In this paper, we investigate the literature regarding sound to capture the intended signal features, and that these production techniques on acoustic wind instruments. translate well into the character of the output signal. A Using this knowledge as a background, we build a simple short performance was recorded to demonstrate that our interface that employs a single microphone to capture the instrument is potentially suitable for live applications. breath signal, which is then processed by an audio plug- in that extracts basic audio features in real time and maps 1. INTRODUCTION them to the parameters of an FM synthesizer. During the late 1970s, breath-controlled electronic instru- ments started to bloom along with digital keyboards. Ya- 2. RELATED WORK maha, Roland and most notably Akai (with their EWI, the electronic wind instrument par excellence), proved them- 2.1 Commercial wind instruments selves to be the leaders in the electronic wind instrument The Akai EWI (Electronic Wind Instrument) is arguably market. Their products try to emulate acoustic wind in- the most popular commercial wind instrument. It has struments (woodwind and brass), according to the diffe- been played by prominent jazz/fusion instrumentalists rent types of interface and playing techniques. They ena- such as Michael Brecker and Bob Mintzer, but also by ble multiple types of output, ranging from physical models more experimental players such as Marshall Allen. The EWI features a clarinet-like form factor, a mouthpiece Copyright: c 2018 Francesco Bigoni et al. This is an open-access article distri- bite sensor, a breath pressure sensor, an internal sound buted under the terms of the Creative Commons Attribution 3.0 Unported License, module, and MIDI capabilities for controlling external which permits unrestricted use, distribution, and reproduction in any medium, pro- synthesizers [2]. The EWI was first invented by Nyle vided the original author and source are credited. Steiner, who earlier released a trumpet-like version called SMC2018 - 134 EVI (Electronic Valve Instrument). Both were later create a mapping from tone hole and embouchure positions licensed to Akai. to the pitch and timbre of a synthesis algorithm. The Yamaha introduced the WX series with the launch of the ANNs were trained by expert performers to generate the WX7 wind instrument in 1987 [3] [4]. Like the EWI, the appropriate mappings. The authors noted that ANN- WX series (now discontinued) included a mouthpiece bite produced mapping improved pitch linearity and continuity sensor for pitch bend. Another major company, Roland, for shifting tone-hole positions. has developed the Aerophone, which mounts an actual The aforementioned examples show several ways of plastic reed on the mouthpiece and a bite sensor analogous mapping multidimensional features such as fingering to the ones employed on the EWI and WX series [5]. The and lip position. However, none of them (except, to plastic reed aims to create a resistance feel analogous to some extent, HIRN) seems to relate inherently to sound that of an actual reed instrument. production techniques that are pertinent to acoustic wind Wind controllers without a dedicated synthesizer module instruments. On the other hand, an enduring lineage of seem to constitute an even smaller niche market. Examples influential saxophone teachers such as Sigurd Rascher, include TE Control USB MIDI Breath Controller [6] and Joe Allard, and Allard’s student Dave Liebman, has Hornberg Research HB1 Breath Station [7], which employ been teaching how to place the articulators in the vocal similar sensor technologies as the aforementioned electro- tract in order to develop a good and personal saxophone nic wind instruments, with added features such as breathe- sound [12]. Extended techniques such as multiphonics in detection (Hornberg) and two-axis accelerometer (TE or growling require an extraordinarily high degree of Control). The early example of Bill Bernardi’s LYRICON awareness of the vocal tract. In the following, we outline by Computone [8], on the other hand, employs a mem- two studies that are supporting Rascher and Allard’s brane and photo cell to convert the acoustic signal from a approach. saxophone-like instrument (featuring an actual reed, mout- Scavone et al. [1] measured the influence of vocal tract hpiece and keys) to send a control voltage to an external configuration on different saxophone blowing techniques synthesizer module — an interface design that, to our kno- by analysing the transfer function between upstream and wledge, has not been replicated since. downstream acoustic pressures. The terms upstream and downstream refer to the air columns on the upper teeth 2.2 Academic research on wind instruments and reed side of the saxophone mouthpiece respectively. Although commercial electronic wind instruments are Since the placement of microphones into the mouthpiece largely standardized, experimental alternatives can be was difficult due to the small dimensions and the high found in the world of academia. sound pressures reached, the authors employed pressure HIRN by Perry R. Cook exhibits an innovative take transducers instead. Their tests covered both conventional on an electronic wind instrument, where breath pressure and extended registers, pitch bending, multiphonics, as is complemented by an array of other features: bite well as bugling — playing an overtone series without tension, lip tension (through a myoelectric sensor), pitch a change in fingering, by varying the vocal tract when singing or buzzing into the mouthpiece, fingering configuration. The authors demonstrated that vocal tract (through buttons) and spatial position, as well as three formation has a fundamental influence on timbre for a rotation controls – one on the mouthpiece and two on plain sound in the conventional register, but also for the the body – plus a linear slide control for the right hand. outer registers and the extended techniques, which are This configuration, which provides multiple dimensions unplayable without the right placement of the articulators. of expression, is mapped to the parameters of a physical One trial showed that even when a player is asked to pitch- model which combines reed excitation (e.g. clarinet), jet bend by varying their lip pressure exclusively, some degree excitation (e.g. flute) and lip excitation (e.g. trombone), of vocal tract manipulation would still be detected [1]. allowing a continuous variation between these timbral In another study, Scavone et al. measured the frequency qualities , through manipulation of the interface [9]. content of breath pressure signals applied to wind The Pipe by Gary P. Scavone employs a pressure sensor, instruments [13].

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