We don’t think twice about playing music via a computer – we have them in our pockets, and in our homes and offices, with music on tap.
But playing music on a computer was once an almost unthinkable leap of the imagination and the most devilishly difficult programming challenge.
The world’s fourth digital computer was designed and built in Australia by the Council for Scientific and Industrial Research (CSIR, the precursor of the CSIRO). It started life as a dream in 1947, ran its first test program in 1949 and played music in 1950 or 1951.
Initially known as the CSIR Mark 1 – later renamed CSIRAC (the CSIR Automatic Computer) – it was built at the CSIR’s radiophysics division in Sydney.
CSIRAC was a very primitive computer by today’s standards. It was very slow (1,000 cycles per second); it did not have very much memory (about 2KB of RAM and 3KB of disk memory); it filled a room and; it had no display like a modern computer.
Most output from CSIRAC was via punched paper tape that was later converted to text on another machine. The only familiar output device was a speaker (called the hooter), and it was used to track the progress of a program.
Programmers would place a sound at the end of their program so they knew it had ended (this was known as a blurt), or they would program progress-indicator blurts into a program.
Despite being primitive, CSIRAC performed groundbreaking work, including running the calculations to find the centre of our galaxy in 1953, and for the engineering of our first skyscraper building.
CSIRAC was a serial computer, it passed digital bits around one at a time unlike the 32 or 64 bits passed around in parallel in modern computers.
The memory on the CSIRAC was mercury acoustic delay lines. That means a pulse would be put into the memory tube, it would travel to the other end of the tube and be recycled back to the front.
In this way, many bits and digital words could be stored in one tube of mercury. There were about 20 memory tubes functional at any time.
A consequence of using mercury acoustic delay time memory was that each memory access took a different time. This would prove problematic for any time-critical application, such as playing music in real time.
The music makerThe first software engineer or programmer was the mathematician Geoff Hill, who is something of an unsung hero of Australian computing.
Hill came from a very musical family; his mother was a music teacher, his sister a performer and he had perfect pitch. This is crucial, as the way CSIRAC created sounds was by sending raw pulses from the computer data bus to the speaker.
If casually programmed, these pulses would arrive at the speaker at somewhat random times, resulting in the blurting type of sound used by programmers to indicate points in the program’s execution.
Hill would have quickly realised that if he could get the pulses to arrive at a regular time, then he would get a steady pitch. Then, perhaps he could program the notes of a musical scale.
This was an exceedingly difficult task because each memory access took a different time, and the overall clock frequency was only 1,000 cycles a second.
But Hill managed this, and his musical knowledge was invaluable, although on at least one occasion he telephoned his mother late at night and asked her if some notes were in tune while holding the telephone receiver to the computer speaker.
Her response on the first occasion was to scold Hill for playing silly buggers with a comb and a piece of paper and annoying her late and night when his dinner was in the oven! She didn’t understand what was going on.
A simple tuneHill programmed CSIRAC to play various popular tunes of the day, such as Colonel Bogey, Girl with Flaxen Hair and so on. This was natural as the programmers were not musical specialists and were not interested in what using a computer meant for the potential composition and performance of music.
The music was one of CSIRAC’s parlour tricks. Dick McGee remembers it playing music when he started at the CSIRO in April 1951. At Australia’s first computing conference, on August 7-9, 1951, everyone was talking about it afterwards and it caused quite a stir.
Read more here: www.sciencealert.com/this-was-the-first-music-ever-played-on-a-computer