The Music of CSIRAC

Australia's First Computer Music

(This is a very brief extract from a much larger and
more comprehensive document -- available soon.)

Paul Doornbusch pauld@koncon.nl

Table of Contents

Introduction

An Overview of CSIRAC

Music and Technology in the Time of CSIRAC

The Speaker

The Music

Music Reconstruction

Newspaper Reports

Acknowledgments

Sources

Links

Introduction

The Australian built automatic computer, initially known as the CSIR Mk1 and later known as CSIRAC, was one of the world's earliest stored program electronic digital computers. Developed in Sydney in the late 1940s by the Council for Scientific and Industrial Research (CSIR), the CSIR Mk1 ran its first program in November 1949. Trevor Pearcey, an English radio physicist, and Maston Beard, a researcher at the CSIR Radiophysics Laboratory in Sydney designed the CSIR Mk1. The first 'programmer' or real software engineer to work with the CSIR Mk1 was Geoff Hill, a mathematician who assisted with the logical design. Hill, who came from a musical family, programmed the CSIR Mk1 to play popular musical melodies from the very early 1950s. In 1951 the CSIR Mk1 publicly played the tune Colonel Bogey. The CSIR Mk1 was moved to Melbourne in June 1955 and renamed CSIRAC. In Melbourne, the mathematics professor Thomas Cherry programmed CSIRAC to perform music and developed a system and program such that anyone who understood standard musical notation could create a punched paper data tape for CSIRAC to perform that music. The music performed by the CSIR Mk1 may seem crude and unremarkable compared to the most advanced musical developments of the time and with what is possible now, but it is amongst the first computer music in the world and the means of production was at the leading edge of technological sophistication at the time. These first steps of using a computer in a musical sense occurred in isolation and they are interesting because it is the leap of imagination to use the flexibility of a general computer to create music and the programming ingenuity required to achieve that which is significant. CSIRAC took some initial steps in that direction.

CSIRAC as displayed for its 50th birthday celebration, Museum Victoria, 25th November 1999.

An Overview of CSIRAC

Please refer to the main CSIRAC page here: http://www.cs.mu.oz.au/csirac for more complete and detailed information regarding the operation of CSIRAC. Below are a few important points of the machine architecture that are significant for the production of sounds.

CSIRAC was a serial computer with mercury acoustic delay-line memory. To understand something of the operation of CSIRAC, it is important to appreciate that all operations were considered as serial transfers of numbers, or data, from a 'source' to a 'destination'. A source could be a register, a memory location, the accumulator and so on. A destination could be a memory location, a register, the paper tape punch or the speaker and so on. During the transfer, the data could undergo transformation, such as being subtracted. The instruction set partitioned each digital word into a 'destination', a 'source' and a data address. The data address, if it applied to the main (mercury delay line) memory, determined the position, or time, of the data in the delay line. Because the memory was a recirculating delay line and the whole machine architecture was serial, it was required to wait until a particular memory location was available for reading. The memory space was very limited at 768 words in total. Understanding the machine timing issues is the key to understanding how the music was produced. Each memory tube was a delay line, so the data in each position in a memory tube required a different time to access. It was possible to calculate this time and determine how long after the start of a clock or access cycle the data was read. Numbers were placed in specific memory locations in such a way that when they were read out and sent to the speaker, they were pulses with a pre-determined period. In this way a predictable pitch was produced and used to create musical melodies.

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