Bell Labs Digital Synthesizer
Encyclopedia
The Bell Labs Digital Synthesizer, better known as the Alles Machine or Alice, was an experimental additive synthesizer
designed by Hal Alles at Bell Labs
during the 1970s. The Alles Machine used 72 computer controlled oscillators whose output was mixed to produce a number of discrete "voices" for output. The Alles Machine has been called the first true digital additive synthesizer, following on earlier Bell experiments that were partially or wholly implemented as software on large computers. Only one full-length composition was recorded for the machine, before it was disassembled and donated to Oberlin College
's TIMARA department in 1981. Several commercial synthesizers based on the Alles design were released during the 1980s, including the Atari AMY
sound chip
.
, the programmable sound generators, and a number of different input devices. The system was packaged into a large single unit, and weighed 300 pounds – the designers optimistically referred to it as being portable.
The microcomputer was supplied with two 8-inch floppy disk
drives (from Heathkit
, which sold their own LSI-11 machine, the H11) and an AT&T color video terminal. It was connected to a customized analog-to-digital converter
that sampled the inputs at 7 bit resolution 250 times a second. The input devices consisted of two 61-key piano keyboards, four 3-axis analog joysticks, a bank of 72 sliders, and various switches. Any of the controllers could be used to control any parameter, under program control. The inputs were interpreted and then used to generate outputs that were sent to the sound generators as a series of parameters. The bandwidth needed to control the synthesizer was quite limited. The computer could process about 1,000 parameter changes per second before it would bog down in the CPU.
The sound generator was fairly complex, containing 1,400 integrated circuits. The first bank of 32 oscillators were used as master signals, and generally meant the system had up to 32-note polyphony (see below). A second set of 32 oscillators was slaved to one of the masters, generating the first N harmonics, where N was from 1 (first harmonic) to 127. Additionally there were a bank of 32 programmable filters, 32 amplitude multipliers, and 256 envelope generators. All of these signals could be mixed in an arbitrary fashion into a bank of 192 accumulators. These were then sent to one of four 16-bit output channels, and from there to a digital-to-analog converter
for output.
The actual waveforms were generated by looking up the amplitude for a given time from a 64 kWord ROM
-based table. Alles used several tricks in the table in order to reduce the amount of math the system needed to run in the controller CPU. In one instance, a multiplication was avoided by looking up two numbers from the table and subtracting them, as it was noticed the result was the same as a multiplication of two related numbers. Running everything was a set of 255 timers with 16 FIFO
stacks for events. The controller posted events into the queues which were then sorted by timestamp and fed into the generator in order.
Crumar
of Italy and Music Technologies' of New York collaborated to form Digital Keyboards in an effort to re-package the Alles Machine. The result was a smaller two-part system, with a Z-80-based microcomputer and disk drives as one unit, and a single keyboard and limited set of input sliders as the second unit. Known as the Crumar General Development System, or GDS, it was released in 1980 for $30,000. It was sold to studios that needed a flexible system that could guarantee the same performance time after time. Analog synths of the same era were subject to environmental changes in the input controls that meant every performance, even after a short delay, would be different. Wendy Carlos
owned a GDS and used it on the Tron
soundtrack.
Further work on the same basic concept produced the lower-cost Synergy, released in 1981. The Synergy removed the computer component, and re-packaged the entire system into a case with a 77-key keyboard. Another additive synth reached the market at about the same time, the Con Brio ADS200, at the slightly lower price of $20,000. Neither the Con Brio or GDS sold well, while the Synergy managed to find some market share. However, when the famous Yamaha DX7
was released in 1983, it quickly took over the market. The DX7's FM synthesis offered the same basic control over output sound as an additive synth, but could duplicate the effects of many ganged oscillators in as few as two. Its $2,000 price point eliminated any competition from the additive synths. Production of the Synergy ended in 1985.
A final version of the original machine was produced after Digital Keyboards was shut down in early 1985. Digital Keyboards' chief designer, Mercer Stockell, decamped and formed Mulogix with Jim Wright and Jerry Ptascynski. The Mulogix Slave 32 was a Synergy re-packaged into two rack-mount modules with a MIDI interface. The Slave 32 could read and write EPROM cartridges from the Synergy.
Starting in 1984, Atari
started an effort to develop a single-chip implementation of the Alles Machine in their Project GAZA. The resulting AMY 1
chip used 64 oscillators and added noise generators to provide special effects needed in games. However the AMY was never released, and a 3rd party effort to produce a low-cost synth based on the chip ended when Atari threatened a lawsuit.
Additive synthesis
Additive synthesis is a technique of sound synthesis that creates musical timbre by explicitly adding sinusoidal overtones together.The timbre of an instrument is composed of multiple harmonic or inharmonic partials , of different frequencies and amplitudes, that change over time...
designed by Hal Alles at Bell Labs
Bell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...
during the 1970s. The Alles Machine used 72 computer controlled oscillators whose output was mixed to produce a number of discrete "voices" for output. The Alles Machine has been called the first true digital additive synthesizer, following on earlier Bell experiments that were partially or wholly implemented as software on large computers. Only one full-length composition was recorded for the machine, before it was disassembled and donated to Oberlin College
Oberlin College
Oberlin College is a private liberal arts college in Oberlin, Ohio, noteworthy for having been the first American institution of higher learning to regularly admit female and black students. Connected to the college is the Oberlin Conservatory of Music, the oldest continuously operating...
's TIMARA department in 1981. Several commercial synthesizers based on the Alles design were released during the 1980s, including the Atari AMY
Atari AMY
Atari's AMY was a 64-oscillator additive synthesizer implemented as a single-IC sound chip. For a time, AMY was slated to be included in newer versions of the Atari 8-bit family, but this did not occur before development of that line was discontinued...
sound chip
Sound chip
A sound chip is an integrated circuit designed to produce sound . It might be doing this through digital, analog or mixed-mode electronics...
.
Description
The Alles Machine consisted of three main parts; an LSI-11 microcomputerMicrocomputer
A microcomputer is a computer with a microprocessor as its central processing unit. They are physically small compared to mainframe and minicomputers...
, the programmable sound generators, and a number of different input devices. The system was packaged into a large single unit, and weighed 300 pounds – the designers optimistically referred to it as being portable.
The microcomputer was supplied with two 8-inch floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
drives (from Heathkit
Heathkit
Heathkits were products of the Heath Company, Benton Harbor, Michigan. Their products included electronic test equipment, high fidelity home audio equipment, television receivers, amateur radio equipment, electronic ignition conversion modules for early model cars with point style ignitions, and...
, which sold their own LSI-11 machine, the H11) and an AT&T color video terminal. It was connected to a customized analog-to-digital converter
Analog-to-digital converter
An analog-to-digital converter is a device that converts a continuous quantity to a discrete time digital representation. An ADC may also provide an isolated measurement...
that sampled the inputs at 7 bit resolution 250 times a second. The input devices consisted of two 61-key piano keyboards, four 3-axis analog joysticks, a bank of 72 sliders, and various switches. Any of the controllers could be used to control any parameter, under program control. The inputs were interpreted and then used to generate outputs that were sent to the sound generators as a series of parameters. The bandwidth needed to control the synthesizer was quite limited. The computer could process about 1,000 parameter changes per second before it would bog down in the CPU.
The sound generator was fairly complex, containing 1,400 integrated circuits. The first bank of 32 oscillators were used as master signals, and generally meant the system had up to 32-note polyphony (see below). A second set of 32 oscillators was slaved to one of the masters, generating the first N harmonics, where N was from 1 (first harmonic) to 127. Additionally there were a bank of 32 programmable filters, 32 amplitude multipliers, and 256 envelope generators. All of these signals could be mixed in an arbitrary fashion into a bank of 192 accumulators. These were then sent to one of four 16-bit output channels, and from there to a digital-to-analog converter
Digital-to-analog converter
In electronics, a digital-to-analog converter is a device that converts a digital code to an analog signal . An analog-to-digital converter performs the reverse operation...
for output.
The actual waveforms were generated by looking up the amplitude for a given time from a 64 kWord ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
-based table. Alles used several tricks in the table in order to reduce the amount of math the system needed to run in the controller CPU. In one instance, a multiplication was avoided by looking up two numbers from the table and subtracting them, as it was noticed the result was the same as a multiplication of two related numbers. Running everything was a set of 255 timers with 16 FIFO
FIFO
FIFO is an acronym for First In, First Out, an abstraction related to ways of organizing and manipulation of data relative to time and prioritization...
stacks for events. The controller posted events into the queues which were then sorted by timestamp and fed into the generator in order.
Influence
The Alles Machine was highly influential within the industry, but the cost of implementation was so high that it was some time before machines based on its principles were available at a price point most musicians could afford.Crumar
Crumar
Crumar is an Italian company which manufactured synthesizers and keyboards in the 60's, 70s and 80s. Its name is taken from that of its founder, Mario Crucianelli...
of Italy and Music Technologies' of New York collaborated to form Digital Keyboards in an effort to re-package the Alles Machine. The result was a smaller two-part system, with a Z-80-based microcomputer and disk drives as one unit, and a single keyboard and limited set of input sliders as the second unit. Known as the Crumar General Development System, or GDS, it was released in 1980 for $30,000. It was sold to studios that needed a flexible system that could guarantee the same performance time after time. Analog synths of the same era were subject to environmental changes in the input controls that meant every performance, even after a short delay, would be different. Wendy Carlos
Wendy Carlos
Wendy Carlos is an American composer and electronic musician. Carlos first came to notice in the late 1960s with recordings made on the Moog synthesizer, then a relatively new and unknown instrument; most notable were LPs of synthesized Bach and the soundtrack for Stanley Kubrick's film A...
owned a GDS and used it on the Tron
Tron (film)
Tron is a 1982 American science fiction film written and directed by Steven Lisberger, and released by Walt Disney Pictures. It stars Jeff Bridges as the protagonist Kevin Flynn; Bruce Boxleitner in a dual role as security program Tron and Tron's "User", computer programmer Alan Bradley; Cindy...
soundtrack.
Further work on the same basic concept produced the lower-cost Synergy, released in 1981. The Synergy removed the computer component, and re-packaged the entire system into a case with a 77-key keyboard. Another additive synth reached the market at about the same time, the Con Brio ADS200, at the slightly lower price of $20,000. Neither the Con Brio or GDS sold well, while the Synergy managed to find some market share. However, when the famous Yamaha DX7
Yamaha DX7
The Yamaha DX7 is an FM Digital Synthesizer manufactured by the Yamaha Corporation from 1983 to 1986. It was the first commercially successful digital synthesizer. Its distinctive sound can be heard on many recordings, especially Pop music from the 1980s...
was released in 1983, it quickly took over the market. The DX7's FM synthesis offered the same basic control over output sound as an additive synth, but could duplicate the effects of many ganged oscillators in as few as two. Its $2,000 price point eliminated any competition from the additive synths. Production of the Synergy ended in 1985.
A final version of the original machine was produced after Digital Keyboards was shut down in early 1985. Digital Keyboards' chief designer, Mercer Stockell, decamped and formed Mulogix with Jim Wright and Jerry Ptascynski. The Mulogix Slave 32 was a Synergy re-packaged into two rack-mount modules with a MIDI interface. The Slave 32 could read and write EPROM cartridges from the Synergy.
Starting in 1984, Atari
Atari
Atari is a corporate and brand name owned by several entities since its inception in 1972. It is currently owned by Atari Interactive, a wholly owned subsidiary of the French publisher Atari, SA . The original Atari, Inc. was founded in 1972 by Nolan Bushnell and Ted Dabney. It was a pioneer in...
started an effort to develop a single-chip implementation of the Alles Machine in their Project GAZA. The resulting AMY 1
Atari AMY
Atari's AMY was a 64-oscillator additive synthesizer implemented as a single-IC sound chip. For a time, AMY was slated to be included in newer versions of the Atari 8-bit family, but this did not occur before development of that line was discontinued...
chip used 64 oscillators and added noise generators to provide special effects needed in games. However the AMY was never released, and a 3rd party effort to produce a low-cost synth based on the chip ended when Atari threatened a lawsuit.