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Box of Cards: Computer music’s birth into real-time interactions By Jenifer Jaseau MUS 605 History of Electronic Music Dr. Jeffrey Stolet University of Oregon School of Music and Dance Pre-MIDI paper Submitted Winter 2010 Box of Cards Introduction Jaseau 2 The development of computer music began with the innovations of Max Mathews at Bell Telephone Laboratories. His work focused on the controlled generation of sound within a computer, leading to the development of computer-based systems we
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  Box of Cards: Computer music’s birth into real-time interactions By Jenifer Jaseau MUS 605 History of Electronic MusicDr. Jeffrey StoletUniversity of Oregon School of Music and Dance Pre-MIDI paper Submitted Winter 2010  Box of Cards Jaseau 2 Introduction The development of computer music began with the innovations of Max Mathewsat Bell Telephone Laboratories. His work focused on the controlled generation of soundwithin a computer, leading to the development of computer-based systems we use todayin computer-generated interactive music systems. These developments started with the Music-N  series, an early computer sound synthesis software program. The first efforts atdigital synthesis were non-real-time, and after many trials from composers andmodifications from technicians, there became a need for real-time application. TheGROOVE system came out of the Music-N series in response for that need, becoming atemplate for live computer music systems today. These two structures of computer architecture became the basis for all computer systems we use today, including Max/MSPand Kyma. The Beginning Max Mathews began working at Bell Telephone Laboratories in Murray Hill, New Jersey after graduating from M.I.T with a doctoral degree in electrical engineering.In 1957, Mathews worked in the acoustic research department at Bell Laboratoriesdeveloping computer equipment to study telephones. His task was to create a listeningtest for telephones in order to judge the quality of a sound received. He constructed adevice that would convert an analog representation of sound, enabling the sound to bereceived by a computer in binary or electrical form. He then needed an additional deviceto get the sound back out of the computer and into an analog representation of sound thata listener could hear. In this way, he developed a way to store and manipulate sound  Box of Cards Jaseau 3waves in numerical form. Sound, at its simplest component, is time-varying pressure inthe air. How sound is made is dependent on how air pressure varies over time. So then,if a computer can generate a pressure function, then a computer can generate sound bygenerating the sounds pressure function. All that is needed for a computer to make soundis a digital computer, a program, a digital-to-analog converter, and a loudspeaker. Thiscombination of devices comes very close to being a capable source for pressure function.The device he invented became the fundamental seed of all computer music; itwas an analog-to-digital converter, and the digital-to-analog converter (ADC and DACrespectively). He is now known as the “Father of Computer Music” because of the manycontributions he made towards the development and discovery of making sounds with acomputer and for applying digital techniques to speech transmission problems and then tomusic. DAC The DAC takes a binary number (such as 01101) and expands it as the sum of itsdigits and then multiplies it by the power of two. The input part of the converter takesthe five-digit number and represents voltages on five lines going into the switch controls.The number “1” equates a positive voltage, and the number “0” equates a negativevoltage. The switch control will send a positive value when the switch is closed, and anegative value when the switch is open. The switches were transistors 1 , replacing acurrent-to-voltage amplifier with an operational amplifier; the transistors would bemeasured in thousands of Ohms. In order to gain a higher accuracy of a sound, more 1 A term coined by John Pierce, it is a semiconductor device commonly used to amplifyor switch electronic signals  Box of Cards Jaseau 4digits were needed to obtain samples, which could be easily done by adding moreswitches and resistors to the system. 2   ADC The ADC was the equivalent of a DAC with the exception that it needed afeedback mechanism and a programmer, which was a small computer. The ADC hadthree essential components: the comparer, the programmer and the DAC.The ADC would convert sound pressure level variations into a series of discretenumbers by using a current-to-voltage amplifier in a sequence of steps; first, the analogvoltage would be applied to the analog input terminal, then the programmer would set itscalculations to zero for each of the five branches. After five cycles of five decisions fromthe comparer, the five branches would output a digital equivalent of the analog input.The ADC was n times slower than the DAC ( n representing the number of digits.) It hadlimitations from n sequential decisions involved in converting a single number.Then there was the question of storage, an essential component of creatingcomputer music. Accessibility to recall digital data within the limits of the system wasanother primary concern. It was essential to the quantization process to maintain asteady sampling rate, for if there were any variations in the sampling rate, it would thenequate to fluctuations similar to wow and flutter in the analog domain. The numbers of samples were greater than the magnetic core memory of a computer so the computer would store samples in bulk. Samples were stored and retrieved in sequence by a digitalmagnetic tape that would record in bulk or groups called records , and these records 2 Mathews, Technology of Computer Music, 26
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