Yamaha Mk100 Portasound

This 1983 Yamaha PortaSound embodies the charming, early '80s pop organ aesthetic, with its warm, vintage tone. It’s a standout among portable keyboards of its era, particularly for features like the "duet" and "trio" modes that layer sounds, and its "stereo symphonic" effect, which simulates a pseudo-Leslie speaker, perfect for capturing the spirit of WERSI Helios or Yamaha Electone organ performances by artists like Klaus Wunderlich and Franz Lambert. While its synthesizer functions are somewhat basic-offering preset envelopes and waveforms-it still delivers a rich, nostalgic sound. Unfortunately, it lacks the organ volume pedal jack found on earlier PortaSounds, though this could potentially be added. Additionally, it boasts a sequencer and programmable drum machine with quirky electronic percussion, ideal for creative experimentation, even in modern techno music.
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Main Features:
Keys: 49 mid-sized keys
Sound: Mono output, enhanced by a "stereo symphonic" Leslie simulator with two speed settings
Polyphony: 8-note (reduced when duet/trio or melody mixer modes are active)
Preset Sounds: 12 semi-OBS orchestra sounds (e.g., organ, trumpet, saxophone, piano, harpsichord, synth) selected via 6 locking buttons with a bank switch
Preset Rhythms: 12 semi-OBS rhythms (e.g., disco, swing, samba, waltz) with 3 bass and chord variations for each
Sound & Rhythm Controls: Locking buttons to select sounds, rhythms, and sustain (off, depth 1, depth 2)
Effects: Vibrato and rhythm fill-in, with a fingered and single-finger accompaniment mode
Sliders: Master volume, tempo, and bass/rhythm volume (5-step switches)
Transpose: Knob adjustable (-5 to +6 semitones)
Custom Drummer: All rhythms and accompaniments are reprogrammable
Multi-Menu: Features 12 buttons and a mechanical 9-page scroll menu for selecting functions
Synthesizer: Allows reprogramming of orchestra sounds, each comprising 2 sub-oscillators with 4 preset envelopes and waveforms. Each sound can toggle vibrato.
Melody Mixer: Layer additional sounds onto the highest held note
Accompaniment: Bass and chord voices can be chosen from any orchestra sound
Sequencer: Multi-track (melody, chord, bass) with cassette saving capability
Sound Generation: Static digital waveforms + envelope, though some sample aliasing is noticeable at lower tones. Drums have a squarewave-like quality.
Output: Mono, post-processed via analog Leslie simulator. The circuit board is quite complex, comparable to that of a C64 home computer.
Connectivity: Line out, headphone jack, AC adapter, and data cassette jacks.
Battery Backup: RAM retention for saved settings
The unique "Multi-Menu" is particularly notable. Functions are selected via a rotating plastic prism, navigated by turning a knob, and confirmed by LED indicators. This menu system was used in other Yamaha products like the Electone home organs. However, later models like the Yamaha PSS-470 rebranded the "Multi-Menu" without the iconic prism, using simpler buttons and sliders instead.