The Split-8 is a

polyphonic Polyphony ( ) is a type of musical texture consisting of two or more simultaneous lines of independent melody, as opposed to a musical texture with just one voice ( monophony) or a texture with one dominant melodic voice accompanied by chords ...

analogue keyboard synthesizer manufactured by

Sequential Circuits Sequential is an American synthesizer company founded in 1974 as Sequential Circuits by Dave Smith. In 1978, Sequential released the Prophet-5, the first programmable polyphonic synthesizer, which was widely used in the music industry. In the ...

. Built in Japan and going by the alternative name Pro-8 in some markets, this was one of the last synthesizers produced by the company and was assigned model number 608. It was released in 1985 at a list price of $1,199 (or $1,195; this number varied between advertisements). This and some other

synthesizers (the

Six-Trak The Six-Trak was an analogue synthesizer manufactured by Sequential Circuits in San Jose, California and released in January 1984, notable for being one of the first multi-timbral synthesizers. It is a six-voice polyphonic synthesizer with one ...

, Multi-Trak and MAX) were built around the

Curtis Electromusic Doug Curtis (March 8, 1951 – January 10, 2007) was the founder of Curtis Electromusic Specialties and OnChip Systems. Curtis was the designer of many original analogue ICs, used in a number of notable electronic music instruments. He was descri ...

CEM 3394 "synth-on-a-chip"

integrated circuit An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...

, and used a

Z80 The Zilog Z80 is an 8-bit microprocessor designed by Zilog that played an important role in the evolution of early personal computing. Launched in 1976, it was designed to be software-compatible with the Intel 8080, offering a compelling altern ...

as their central

microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...

Features and Cabinet

Brief Summary of Features

This

electronic keyboard An electronic keyboard, portable keyboard, or digital keyboard is an electronic musical instrument based on keyboard instruments. Electronic keyboards include synthesizers, digital pianos, stage pianos, electronic organs and digital audio work ...

is an 8-voice

, bi-timbral

analogue synthesizer An analog synthesizer () is a synthesizer that uses analog circuits and analog signals to generate sound electronically. The earliest analog synthesizers in the 1920s and 1930s, such as the Trautonium, were built with a variety of vacuum-tube (t ...

with the ability to split or layer two sounds ("double" mode). It has 64 memory locations for sounds (" patches"). Patches may be "linked" in memory so that calling up one automatically calls up the second for a split or layer. A

monophonic Monaural sound or monophonic sound (often shortened to mono) is sound intended to be heard as if it were emanating from one position. This contrasts with stereophonic sound or ''stereo'', which uses two separate audio channels to reproduce sou ...

mode, with all eight oscillators producing the same sound at once, is also possible. Polyphonic

portamento In music, portamento (: ''portamenti''; from old , meaning 'carriage' or 'carrying'), also known by its French name glissade, is a pitch sliding from one Musical note, note to another. The term originated from the Italian language, Italian exp ...

is also available. The instrument features

MIDI Musical Instrument Digital Interface (; MIDI) is an American-Japanese technical standard that describes a communication protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, ...

, including the capability to save and restore patches with system-exclusive data (see

for more detail about this process).

Front Panel

The front panel has two

volume Volume is a measure of regions in three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch) ...

knobs (one for each available sound), a master tuning knob, a data entry knob for programming patches, modulation and pitch wheels, various buttons for mode (layer, or "double", split) and program selection, and a four by eight grid for programming (with all parameters labelled on the grid; see Figure 1). Some other functions are also listed on the panel as a reminder of which buttons to press. The case is metal with light blue graphics and lettering, red

LED A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresp ...

indicators, and black painted wooden end pieces.

Back Panel

The back panel has quarter-inch jacks for recording data to

cassette tape The Compact Cassette, also commonly called a cassette tape, audio cassette, or simply tape or cassette, is an analog audio, analog magnetic tape recording format for Sound recording and reproduction, audio recording and playback. Invented by L ...

(one also doubling as a footswitch input),

in and out

DIN connector The DIN connector is an electrical signal connector that was standardized by the (DIN), the German Institute for Standards, in the mid 1950s, initially with three pins for mono, but when stereo connections and gear appeared in the late 1950s, v ...

s, separate quarter-inch audio outputs for each of the two sounds and a mix audio out (both sounds combined), a power switch, and a

fuse Fuse or FUSE may refer to: Devices * Fuse (electrical), a device used in electrical systems to protect against excessive current ** Fuse (automotive), a class of fuses for vehicles * Fuse (hydraulic), a device used in hydraulic systems to protec ...

socket.

Keyboard

The keyboard is five

octaves In music, an octave (: eighth) or perfect octave (sometimes called the diapason) is an interval between two notes, one having twice the frequency of vibration of the other. The octave relationship is a natural phenomenon that has been referr ...

(61 notes, C to C) and is unweighted. It has no velocity or

aftertouch Keyboard expression is the ability of a keyboard musical instrument to change tone or other qualities of the sound in response to velocity, pressure or other variations in how the performer depresses the keys of the musical keyboard. Expression ...

sensitivity.

Voice Architecture and Sound Programming

Voice Architecture

The synthesizer voices are based on the Curtis Electronics CEM 3394 chip. This allows for one

voltage-controlled oscillator A voltage-controlled oscillator (VCO) is an electronic oscillator whose oscillation frequency is controlled by a voltage input. The applied input voltage determines the instantaneous oscillation frequency. Consequently, a VCO can be used for fre ...

(VCO) per voice, with on/off toggles for any combination of sawtooth, triangle and variable pulse

waveforms In electronics, acoustics, and related fields, the waveform of a signal is the shape of its graph as a function of time, independent of its time and magnitude scales and of any displacement in time.David Crecraft, David Gorham, ''Electroni ...

. There are coarse (up to 4

) and fine (to just under a

semitone A semitone, also called a minor second, half step, or a half tone, is the smallest musical interval commonly used in Western tonal music, and it is considered the most dissonant when sounded harmonically. It is defined as the interval between ...

) tuning parameters. A "poly mod" parameter allows the audio output of one voice to feed another's

voltage-controlled filter A voltage-controlled filter (VCF) is an electronic filter whose operating characteristics (primarily cutoff frequency) can be set by an input control voltage. Voltage-controlled filters are widely used in synthesizers. A music synthesizer VCF ...

(VCF) when they are layered in "double" mode. This results in a sound with 4-voice polyphony with no audio from the second voice's oscillators, processed through two filters in series. The single

low-frequency oscillator Low-frequency oscillation (LFO) is an electronic frequency that is usually below 20 Hz and creates a rhythmic pulse or sweep. This is used to modulate musical equipment such as synthesizers to create audio effects such as vibrato, tremolo ...

(LFO) is free-running (i.e. doesn't restart when a key is depressed), with programmable rate (0.25 to 20 Hz according to the manual), and has programmable depth and

waveform In electronics, acoustics, and related fields, the waveform of a signal is the shape of its Graph of a function, graph as a function of time, independent of its time and Magnitude (mathematics), magnitude Scale (ratio), scales and of any dis ...

(triangle or square). This can modulate any combination of filter

cutoff frequency In physics and electrical engineering, a cutoff frequency, corner frequency, or break frequency is a boundary in a system's frequency response at which energy flowing through the system begins to be reduced ( attenuated or reflected) rather than ...

, pitch, or oscillator pulse-width. There is a

chorus Chorus may refer to: Music * Chorus (song), the part of a song that is repeated several times, usually after each verse * Chorus effect, the perception of similar sounds from multiple sources as a single, richer sound * Chorus form, song in whic ...

with fixed rate and frequency. Filter

, resonance (to self-oscillation), keyboard tracking (off, half or full) and envelope amount can be programmed, but the envelope cannot be inverted. The two

ADSR envelope In sound and music, an envelope describes how a sound changes over time. For example, a piano key, when struck and held, creates a near-immediate initial sound which gradually decreases in volume to zero. An envelope may relate to elements such ...

s modulate the VCA and the 24 dB/octave VCF. The rate for the polyphonic

is programmable. "Unison" (

mode) can be programmed for each patch. In this mode, the envelopes are re-triggered only after all keys are released ("legato", with low-note priority), and a delay of four oscillators relative to the other four can be programmed (fixed at 20, 40 or 80 milliseconds). A program can be "linked" to another so that both are called up and assigned correctly in a split or layer. There is also a programmable output level for each patch to help balance loud and soft sounds.

Performance Controls

There are separate volume knobs for channels A and B (i.e. the two patches in a split or layer). The footswitch can be programmed to momentarily change patches, or change one of several patch parameters: filter

amount or attack; VCA decay or release; voice volume (the momentary value of any of the preceding being user-defined); chorus on/off, or portamento on/off. The parameter value knob can be used to alter one parameter in real-time, although the value will "jump" to the knob's current setting as soon as it is moved and some parameters stairstep badly when treated this way. The pitch-bend wheel is not spring-loaded and is centre-detented. Oscillator tuning can be initiated from the front panel, with this process taking about twenty seconds. During tuning, the instrument is silenced.

MIDI Implementation

The Split-8 has quite advanced

implementation for an instrument of this vintage. OMNI mode, wheel controller reception/transmission and program change can be toggled on or off. All MIDI operation (in and out) can be disabled, and there is the capability for saving and loading patches. The MIDI receive channel (1-16) can be set for each patch. Four voices can be assigned to one patch that is controlled only via MIDI, with the other four playing a patch controlled only from the keyboard. In this case, wheel effects can be disabled for the MIDI-controlled patch. The Split-8 also recognizes incoming pitch-bend and modulation wheel data as well as note number, note on and off, program change, and tuning request. Some

functions are accessed through a special "MIDI Expand" mode. This is entered by holding down the RECORD button and pressing PROGRAM SELECT 5. All of the LEDs for the PROGRAM SELECT buttons blink, and pressing one of these PROGRAM SELECT buttons now performs one of the following: # Selects MIDI mode 1 (OMNI on/poly). If the instrument is in SPLIT mode, data from the MIDI in port will be passed to both programs (as though the synth were in DOUBLE mode). This is the reverse of using button 3, below. # Initiates a 2,240 byte system exclusive dump consisting of patch data. The

for PROGRAM SELECT 2 remains lit during the few seconds that this takes. # Selects MIDI mode 3 (OMNI off/poly). This is the reverse of using button 1, above. # Not used. # Toggles between enable and disable of program changes. Transmission and reception of program changes via MIDI is disabled by default when the synthesizer is switched on. # Toggles between enable and disable of both the pitch-bend and modulation wheels. On power-up, MIDI transmission and reception for both is disabled by default. When sending

program (system-exclusive) information to the Split-8, the 64 patches are sent as a string of single-patch packets, so loading single patches at a time is possible. When sending all 64, the synthesizer will sporadically "lose" some patches, presumably because it cannot handle

data transmitted at the speed that modern computers can send it. Most music software allows the user to insert a short delay between packets of sysex information, circumventing this problem. A 50 millisecond delay is adequate. According to the manual, it is possible to have the Split-8 respond to a system-exclusive dump-request, but the manual does not indicate what the request bytes are, nor is there a byte-map of the sysex data. The Split-8 does not respond to the

"all notes off" message, and pitch-bend depth is fixed at +/- a

major third In music theory, a third is a Interval (music), musical interval encompassing three staff positions (see Interval (music)#Number, Interval number for more details), and the major third () is a third spanning four Semitone, half steps or two ...

Other information

Use in Recorded Music

An audio sampling CD entitled “Astral Ambience”, produced by Martin Newcomb of the Museum of Synthesizer Technology, features a large list of vintage synthesizers, including the Split-8. The CD was very favourably reviewed in the June 1996 issue of

Keyboard magazine ''Keyboard'' is a magazine that originally covered electronic keyboard instruments and keyboardists, though with the advent of computer-based recording and audio technology, they have added digital music technology to their regular coverage, in ...

, although no explicit mention is made of the Split-8 sounds.

Spare Parts and Manuals

A source of spare parts and manuals for the Split-8 i
Wine Country Productions
They also have Split-8 owner’s manuals and

cassette Cassette may refer to: Technology * Cassette (format) (or ''cassette tape''), a format that contains magnetic tape for audio, video, and data storage and playback * Compact Cassette, a worldwide standard for analog audio recording and playback ...

tapes of the original preset sounds (data that can be uploaded into the instrument).

Literature

Advertisements of about a third of a page in size can be found in contemporary issues of

Keyboard Magazine ''Keyboard'' is a magazine that originally covered electronic keyboard instruments and keyboardists, though with the advent of computer-based recording and audio technology, they have added digital music technology to their regular coverage, in ...

. The owner's manual and service schematics are available fro
Wine Country Productions
The Split-8 appears in the price lists at the end of both editions of Mark Vail’s ''Vintage Synthesizers'', although it is not mentioned elsewhere. There is also a capsule summary of the Split-8 in ''The A-Z of Analogue Synthesizers'' that contains numerous inaccuracies. The more recent edition of this book may be more accurate.

Software and Sounds

The Split-8 was supported by Opcode's Galaxy universal librarian software, which is no longer available. Original factory presets were written by sound designer John Bowen

, June 1985. and are available on

fro
Wine Country Productions

Reference Material

References

Other sources

* Split-8 marketing brochure, Sequential Circuits, 1985 * Split-8 user's manual * Split-8 service schematics * Sequential Suggested Retail Price List, SCI 3/85, 1985 {{Sequential Circuits Sequential Circuits synthesizers Polyphonic synthesizers Analog synthesizers