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

Click to access Alles_synth_1977.pdf

‘GROOVE Systems’, Max Mathews & Richard Moore, USA 1970

Max Mathews with the GROOVE system
Max Mathews with the GROOVE system

In 1967 the composer and musician Richard Moore began a collaboration with Max Mathews at Bell Labs exploring performance and  expression in computer music in a ‘musician-friendly’ environment. The result of this was a digital-analogue hybrid system called GROOVE  (Generated Realtime Operations On Voltage-controlled Equipment) in which a musician played an external analogue synthesiser and a computer monitored and stored the performer’s manipulations of the interface; playing notes, turning knobs and so-on. The objective being to build a real-time musical performance tool by concentrating the computers limited power, using it to store musical parameters of an external device rather than generating the sound itself :

“Computer performance of music was born in 1957 when an IBM 704 in NYC played a 17 second composition on the Music I program which I wrote. The timbres and notes were not inspiring, but the technical breakthrough is still reverberating. Music I led me to Music II through V. A host of others wroteMusic 10, Music 360, Music 15, Csound and Cmix. Many exciting pieces are now performed digitally. TheIBM 704 and its siblings were strictly studio machines–they were far too slow to synthesize music in real-time. Chowning’s FM algorithms and the advent of fast, inexpensive, digital chips made real-time possible, and equally important, made it affordable.”
Max Mathews. “Horizons in Computer Music,” March 8-9, 1997, Indiana University

Richard Moore with the Groove System
Richard Moore with the Groove System

The system, written in assembler, only ran on the Honeywell DDP224 computer that Bell had acquired specifically for sound research. The addition of a disk storage device meant that it was also possible to create libraries of programming routines so that users could create their own customised logic patterns for automation or composition. GROOVE allowed users to continually adjust and ‘mix’ different actions in real time, review sections or an entire piece and then re-run the composition from stored data. Music by Bach and Bartok were performed with the GROOVE at the first demonstration at a conference on Music and Technology in Stockholm organized by UNESCO  in 1970. Among the participants also several leading figures in electronic music such as Pierre Schaffer and Jean-Claude Risset.

“Starting with the Groove program in 1970, my interests have focused on live performance and what a computer can do to aid a performer. I made a controller, the radio-baton, plus a program, the conductor program, to provide new ways for interpreting and performing traditional scores. In addition to contemporary composers, these proved attractive to soloists as a way of playing orchestral accompaniments. Singers often prefer to play their own accompaniments. Recently I have added improvisational options which make it easy to write compositional algorithms. These can involve precomposed sequences, random functions, and live performance gestures. The algorithms are written in the C language. We have taught a course in this area to Stanford undergraduates for two years. To our happy surprise, the students liked learning and using C. Primarily I believe it gives them a feeling of complete power to command the computer to do anything it is capable of doing.”
Max Mathews. “Horizons in Computer Music,” March 8-9, 1997, Indiana University

The GROOVE System at the Bell Laboratories circa 1970
The GROOVE System at the Bell Laboratories circa 1970

The GROOVE system consisted of:

  • 14 DAC control lines scanned every 100th/second ( twelve 8-bit and two 12-bit)
  • An ADC coupled to a multiplexer for the conversion of seven voltage signal: four generated by the same knobs and three generated by 3-dimensional movement of a joystick controller;
  • Two speakers for audio sound output;
  • A special keyboard to interface with the knobs to generate On/Off signals
  • A teletype keyboard for data input
  • A CDC-9432 disk storage;
  • A tape recorder for data backup

Antecedents to the GROOVE included similar projects such as PIPER, developed by James Gabura and Gustav Ciamaga at the University of Toronto, and a system proposed but never completed by Lejaren Hiller and James Beauchamp at the University of Illinois . GROOVE was however, the first widely used computer music system that allowed composers and performers the ability to work in real-time. The GROOVE project ended in 1980 due to both the high cost of the system – some $20,000, and also  to advances in affordable computing power that allowed synthesisers and performance systems to work together flawlessly .


Joel Chadabe, Electric Sound: The Past and Promise of Electronic Music, Prentice Hall, 1997.

F. Richard Moore, Elements of Computer Music, PTR Prentice Hall, 1990.