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.