Bell Labs Hal Alles Synthesiser, Hall Alles, USA, 1976.

Hal Alles Synthesiser
Hal Alles Synthesiser. (Image; Computer Music Journal Vol1 Number 4.)

The ‘Bell Labs Digital Synthesiser’ or ‘Hal Alles Synthesiser’ was one of the first ‘real-time’ digital instrument – as opposed to a non-real time digital/analogue hybrid performance such as the GROOVE system. The instrument was the result of Alles’ experiments with digital filters and tone generators for telephonic applications at Bell Labs (Murray Hills, New Jersey, USA) during the mid 1970’s.

Alles was tasked with ‘selling in’ the fruits of his digital telephony research to a Bell Labs internal audience and he discovered that – despite his complete lack of musical ability – his job became much easier if he included real-time synthesised music in his presentations:

“As a research organization (Bell labs), we had no product responsibility. As a technology research organization, our research product had a very short shelf life. To have impact, we had to create “demonstrations”. We were selling digital design within a company with a 100 year history of analog design. I got pretty good at 30 minute demonstrations of the real time capabilities of the digital hardware I was designing and building. I was typically doing several demonstrations a week to Bell Labs people responsible for product development. I had developed one of the first programmable digital filters that could be dynamically reconfigured to do all of the end telephone office filtering and tone generation. It could also be configured to play digitally synthesized music in real time. I developed a demo of the telephone applications (technically impressive but boring to most people), and ended the demo with synthesized music. The music application was almost universally appreciated, and eventually a lot of people came to just hear the music.”

Max Mathews – creator at Bell Labs of the MUSIC X series of computer synthesis languages – witnessed one of these demonstrations and excitedly encouraged Alles to develop the a musical instrument using purely digital technology.

“The goal was to have recording studio sound quality and mixing/processing capabilities, orchestra versatility, and a multitude of proportional human controls such as position sensitive keyboard, slides, knobs, joysticks, etc. It also needed a general purpose computer to configure, control and record everything. The goal included making it self-contained and “portable”. I proposed this project to my boss while walking back from lunch. He approved it before we got to our offices. “

With no background in music technology, Alles, inspired and intrigued by Robert Moog’s recent instruments and Carlos’s ‘Switched on Bach’  began to assemble the new digital synthesiser in the mid-1970’s; a ‘fragile laboratory one-off of questionable reliability’.

However, Once completed, the Alles Synthesizer project was sidelined in favour of more business oriented research and was little used apart from internal presentations. This changed in 1977 when Bell Labs and AT&T used the instrument as the centerpiece for the Motion Picture Academy’s 50th anniversary celebration of talking pictures.

Doug Bayer (a Bell Labs software researcher) was brought in to improve the human interface and operating system and the rather delicate instrument was flown to Hollywood where – Roger Powell (Todd Rundgren’s Utopia, David Bowie band and later Apple Computers Audio lab)– was hired to perform in front of a live audience. The video below was recorded to be shown if the instrument broke down before the show:

Despite a renewed interest from the music industry, Alles moved to other fields of research at Bell labs, Max Mathews worked with the machine for a while and in 1981 it was donated to Oberlin College Conservatory TIMARA department  where it has recently been rebuilt using modern components.

Description of the Hal Alles Synthesiser from the Computer Music Journal Volume 1 Number 3 (Fall 1976)

A Portable Digital Sound Synthesis System
H. G. Alles Bell Laboratories ‘
Murray Hills New Jersey 07974

The Hal Alles Synthesiser consisted of three units;

1. A DEC LS1-11 micro-computer with two floppy discs, a 64k word ROM mapable memory for table look-up  and i/o buffering and an ASCII AT&T colour graphics monitor with full ASCII keyboard.Since there are no hard-wired connections between the input devices and the synthesizer hardware, and since synthesizer interconnections are accomplished through program loaded control registers, the whole system may be used in a variety of ways. For example:A. All the control parameters may be specified in real time and at performance time.B. Several files may be prepared in real time but before the performance. Then at performance time, the files may be played with some subset of the control parameters supplied during the performance.C . Files may be prepared and/or edited in nonreal time, incrementally improving the original performance.2. A Sound generator banks; consisting of 64 oscillators. The first set of 32 oscillators were used for sound generation – giving a potential 32 note polyphony. The second set of 32 oscillators were used to create the harmonics of the sound generation oscillators. The waveforms of the sound were created by looking up amplitude from the 64k word ROM table. In addition to the sound generators were a bank of 32 programmable filters, 32 amplitude multipliers, and 256 envelope generators. All of these signals could be mixed to one of four 16-bit output channels, and from there to a digital-to-analog converter for output.3. various input devices; including two 61 note keyboard manual – giving two part multitimbrality, four 3-axis analog joysticks and a bank of 72 slider pots. These controllers could be used –within the computers limited bandwidth of around 1,000 parameter changes per second –to make real-time changes to the parameter of the sound generators and allowing the instrument to be able to deliver ‘100 reasonably complex notes per second’(Alles. Computer Music Journal Vol.1 Number 4.)


Alles’s instrument had significant but quiet influence on the development of electronic instruments, most notably the Italian company Crumar’s high-end GDS ‘General Development System’ which was essentially a commercially repackaged version of the Alles Synthesiser released in 1980 . The GDS was a 16-bit digital synthesizer with 32 oscillators offering a mix of both additive and FM/Phase Distortion synthesis and consisted of the sound generator and keyboard unit controlled by a  Z-80-microcomputer. With a hefty price tag of around $30,000, the GDS was intended as a general music production system for recording studios giving consistent and real time performance capabilities far beyond the rather erratic analog synthesisers of the day. Wendy Carlos was an early (and current) champion of the GDS.

Wendy Carlos. A soundtrack  example of the Crumar GDS on the theme from ‘Tron’ 1982.

As the components used in the prototype eventually became cheaper, more cost effective versions were produced such as the DKI (Crumar again) Synergy, released in 1981 for around $5,300, this instrument disposed of the external computer in favour of a much simplified push-button interface (or an optional Kaypro 2 computer) and housed the entire instrument in a more conventional keyboard housing. In 1981  Ceasar Castro and Alan Heaberland produced their Casheab S-100 system clearly influenced by the Alles Synthesiser design. The Japanese computer company Atari initiated the Sierra Project; a 64 oscillator single chip version of the Alles synthesiser intended for games effects and music – known as the AMY1 chip it never saw the light of day due to legal difficulties.

A Crumar GDS restored by Dan Wilson, Hideaway Studio
A Crumar GDS restored by Dan Wilson, Hideaway Studio

Ultimately all of these early digital additive/FM instruments and projects were rendered obsolete by the arrival of Yamaha’s affordable digital DX7 FM Synthesiser in 1983. Production of the Synergy finished in 1985 – though a rack mounted MIDI version (by Mercer Stockell, Jim Wright and Jerry Ptascynski)  called the  Mulogix Slave 32 was produced until 1989.

image: Popular Science Magazine, USA,  January 1978
image: Popular Science Magazine, USA,  January 1978

Sources & Bibliography

Interview with Hal Alles. October 2017 by Simon Crab.

Chadabe, Joel .”Electric Sound”, Prentice Hall, 1997, pg. 178

Alles, Hal,, “A Portable Digital Sound Synthesis System”, Computer Music Journal, Volume 1 Number 3 (Fall 1976), pg. 5-9

Alles, Hal, (Alles 1979), “An Inexpensive Digital Sound Synthesizer”, Computer Music Journal, Volume 3 Number 3 (Fall 1979), pg. 28-37

Alles, Hal, “Music Synthesis Using Real Time Digital Techniques”, Proceedings of the IEEE, Volume 68 Number 4 (April 1980), pg. 436–449

Manning, Peter “Electronic and Computer Music”, Oxford University Press US, 2004