Modern Api Design and Physical Computing Techniques in Just
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MODERN API DESIGN AND PHYSICAL COMPUTING TECHNIQUES IN JUST INTONATION PERFORMANCE PRACTICE Mark Sonnabaum Thesis Prepared for the Degree of MASTER OF ARTS UNIVERSITY OF NORTH TEXAS May 2013 APPROVED: Joseph Klein, Major Professor and Chair of the Division of Composition Studies Robert Akl, Minor Professor Jon Christopher Nelson, Committee Member John Murphy, Interim Director of Graduate Studies in the College of Music James Scott, Dean of the College of Music Mark Wardell, Dean of the Toulouse Graduate School Sonnabaum, Mark. Modern API Design and Physical Computing Techniques in Just Intonation Performance Practice. Master of Arts (Music ), May 2013, 48 pp., 16 figures, references, 18 titles. Music that uses just intonation has been historically difficult to perform. Using modern instruments and custom built instruments both have different sets of advantages and disadvantages. This paper explores how the problem has been approached previously by both Harry Partch and Ben Johnston, and proposes the decoupling of interface and sound production as a way forward. The design and implementation of a software instrument and a hardware prototype are described, both using a simple API for variable tuning instruments. The hardware prototype uses physical computing techniques to control the tuning of a string with a servo motor, while the software instrument exists entirely in a web browser. Finally, potential algorithms for clients of the API are presented, and the effectiveness of the hardware prototype is evaluated by measuring its pitch accuracy. Copyright 2013 by Mark Sonnabaum ii TABLE OF CONTENTS Page LIST OF FIGURES .......................................................................................................... iv CHAPTER 1. INTRODUCTION ....................................................................................... 1 CHAPTER 2. JUST INTONATION PERFORMANCE ..................................................... 2 CHAPTER 3. INSTRUMENT DESIGN .......................................................................... 14 Dynamically Tunable Bridge ............................................................................... 16 OSC as an Interface ........................................................................................... 17 CHAPTER 4. IMPLEMENTATION ................................................................................ 19 API ...................................................................................................................... 19 Software Instrument ........................................................................................... 21 Hardware Instrument .......................................................................................... 25 CHAPTER 5. TESTING ................................................................................................. 28 Hardware Testing ............................................................................................... 28 Client Software Application ................................................................................. 33 CHAPTER 6. FURTHER IDEAS AND POTENTIAL IMPROVEMENTS ........................ 35 Hardware ............................................................................................................ 35 Software ............................................................................................................. 35 APPENDIX: CODE SAMPLES ...................................................................................... 39 REFERENCES .............................................................................................................. 47 iii LIST OF FIGURES Page 2.1 Johnson’s tuning system ...................................................................................... 8 3.1 Steel guitar rods ................................................................................................. 16 3.2 Steel guitar changer ........................................................................................... 17 4.1 MIDI note numbers to frequency offset ............................................................... 20 4.2 Five-limit API example ........................................................................................ 21 4.3 Software instrument user interface ..................................................................... 23 4.4 Note class .......................................................................................................... 24 4.5 Prototype body ................................................................................................... 26 4.6 Hammer/damper diagram ................................................................................... 27 5.1 Ball link end attached to tuning bar ..................................................................... 28 5.2 Tuning bridge...................................................................................................... 29 5.3 Roller bridge ....................................................................................................... 30 5.4 Tuning bar test script .......................................................................................... 31 5.5 Tuning bar test pitch analysis ............................................................................. 32 5.6 Key detection example ...................................................................................... 34 6.1 Tonality example ................................................................................................ 36 iv CHAPTER 1 INTRODUCTION The performance of music using just intonation is problematic for a number of rea- sons, not least of which is the fact that modern instruments are often designed for equal temperament and performers are trained to fight against the justly intonated characteris- tics their instrument may have. Most well known composers who have attempted to solve this problem have done so in very different ways. Because issues lie with both performers and the use of modern instruments, a common approach has been to focus largely on one area or the other, which has mixed results. In this paper, I discuss historical precedents in the area of just intonation perfor- mance, specifically focusing on the work of Harry Partch and Ben Johnston. Both com- posers have approached this problem differently due to skill sets or available technologies, so I highlight the most effective methods in each case and how we can learn from them. My approach to this topic involves the use of a simple application programming interface to facilitate the use of both software modeling and physical computing techniques to achieve the level of pitch accuracy necessary for just intonation music. It is my belief that developing standard interfaces and tools that address these technical challenges will allow a greater number of composers and musicians to explore the rich musical possibilities of extended just intonation. 1 CHAPTER 2 JUST INTONATION PERFORMANCE Unlike many musical trends in the twentieth century, composing using just intona- tion is neither a way to break free of tonality nor an attempt to return to it. It is inherently free of the western European musical associations that so many composers try to exorcise from their musical consciousness, simply because it’s neither a genre, style, nor a school, all of which are ephemeral, but rather a musical foundation. Its practice is as ancient as music itself because it is based on the two musical phenomena, which are absolutely unchangeable: an object’s ability to produce sound as it vibrates, and the human ear’s ability to perceive it.1 As a musical system, its rationale is irrefutable, although a modern composer’s implementation of this system in his or her music tends to require a bit more conviction, if not downright evangelism. Because each composer who either experiments with or dedicates himself to using just intonation will likely use it differently in his or her mu- sic, most of this music will get broadly classified as “microtonal.” Even the most educated performers will likely find this method of developing scales and harmonies by adding and subtracting whole number ratios to be confusing. The fact that there is no standard set of pitches, which can change with each composer (or piece), makes it even more difficult to understand as a whole. This alone is likely to intimidate most performers, who will not want to commit to learning the theory behind your system of tuning, becoming accustomed to the notation, and practicing in this unfamiliar system, only to sound “out-of-tune” to a lay audience. All composers who make the decision to compose in just, or extended just intonation deal with these issues in one way or another. The following section will explore, 1Partch, Genesis of a Music: An Account of a Creative Work, Its Roots, and Its Fulfillments, Second Edition. 2 compare, and contrast two very different approaches to composing and performing us- ing just intonation through two of its most dedicated composers: Harry Partch and Ben Johnston. Partch was initially inspired to develop a system of tuning based on just intonation to closer approximate the human voice. About his early work, Partch writes, “I came to the realization that the spoken word was the distinctive expression my constitutional makeup was best fitted for, and that I needed other scales and other instruments.”2 He then decided to build a new instrument, which would allow him to realize these pitches more easily. He constructed a viola