The Soundchaser Computer Music System by Passport Designs Inc.

The Soundchaser Computer Music System (sometimes “SoundChaser,” by Passport Designs) is an early 1980s Apple II‑based music/hardware/software setup.

Developed by Passport Designs, Inc. a pioneering company in computer music founded in 1979.
Released around 1982. It’s a “pre‑MIDI” system for the Apple II (II/II+ etc.).
The system combines hardware (interface & voice cards, soundsynth boards), a keyboard, and software (sequencer, editor, etc.).
Apple II computer (48 KB RAM) + disk drive + monochrome monitor.
Sound‑generation cards (“voice cards”) installed in Apple II expansion slots. Each card provided three voices of sound on each card. Could have multiple voice cards.
Analogue voice circuitry including low‑pass filter (CEM 3320 VCF), VCA (LM3080), etc. For wave shaping, a square‑wave source was generated via Intel 8253 timers.
Four‑octave keyboard, connected via an interface board. Keys encoded via diode matrix, etc.
“EDIT” software allowing setting up voice parameters (VCF, VCA, envelope etc.) with an interactive display.
Sequencer with multi‑event banks to record/playback sequences from the keyboard.
Support for loading presets (“Sound Definitions”), mixing of two oscillators, envelopes (ADSR etc.).
It was rare a niche / enthusiast product.
It was “pre‑MIDI,” i.e. built before the MIDI standard, so interfacing was proprietary in nature.
It was relatively expensive at the time.

Specs:

• 49 Keys
• Voice Cards One or two three‑voice cards can be added. Each voice card provides 3 voices.
• Oscillator / Waveform Source Uses Intel 8253 timer chips (3 timers, one per voice) driven from Apple II’s 2 MHz system clock; square waves created that way.
• Wave Shaper An analog "wave shaper" (ramp generator) to convert square wave to sawtooth waveform.
• Filter & VCA Analogue circuitry: 24 dB / octave low-pass filter (CEM 3320 VCF) and a VCA based on LM3080 transconductance op-amp.
• Envelope / Modulation Software‑drawn “contours” (control over attack, decay, etc.) – 4 contours can be drawn.
• Some modulation functionality via software.
• Sequencer Multi‑event sequencer with 4 independent banks (in base version) for presets & playback/record, sequences from keyboard.
• Turbo‑Traks (optional module/software) Adds up to 16 tracks; variable number of oscillators per voice; extended recording time; sync to tape/drum machine.
• Preset / Instrument Banks Multiple presets loaded; ability to assign oscillators to presets; split keyboard between presets.
• All control changes (patch parameters) are non‑real‑time for many settings , you often need to draw contours or edit via software rather than tweak live while playing.
• Only one oscillator per voice in the base version; no pulse-width modulation (PWM) or sub‑oscillator mixing in the base voice cards.
• Some quantisation noise and limited signal/noise (S/N) ratio; output bandwidth limitations

Owner's manual

Product specs