http://weltenschule.de/TableHooters/HingHon_EK001.html

This small keyboard is one of the last squarewave keyboards those were made. It was still listed 1999 on Asian Sources. On the box stands only "portable electronic keyboard", though this was the only way to find its manufacturer name Hing Hon and the model name "EK-001". It has unique and very impulsive POKEY percussion. The semi- analogue main voice timbres drone bright, sinister and unusual and have an almost medieval appeal.

This is much more than just a toy; with some modifications you can build a real semi- analogue synthesizer of it. The 2 note polyphonic main voice employs great sonorous multipulse squarewave timbres with partly long decaying analogue volume envelopes. With some modifications it can be transformed into fast C64 arpeggiator- like effect sounds. Although there is no accompaniment, the grainy squarewave based percussion is incredible impulsive and sounds like programmed on the Atari POKEY synthesizer chip. main features: 37 mini keys polyphony 2 notes 8 OBS preset sounds {music box, violin, flute, organ, guitar, banjo, horn, piano} 8 OBS preset rhythms {disco, ballad, march, swing, pop, waltz, rhumba, tango} with unique percussion; some notes have an accent (no accompaniment) 4 drumpad buttons tempo +/- buttons (16 steps) vibrato button (vibrato modulates the CPU clock) master and microphone volume sliders (5 steps) sound generation is squarewave based with capacitor envelope; some sounds use multipulse squarewaves (short bit loops). The CPU in turns sends pulse width modulated currents to the capacitor to charge/ discharge it and between them it measures the actual charge voltage to control the output volume by it (using a sample- and- hold circuit?). Exceptional is the "organ" sound, which is an incredible sinister and massive sounding, powerful church organ variant with much reverberation. The piano sound ignores key press duration. percussion sounds {base, snare, hihat, cowbell} sound very electronic and extremely impulsive and are best comparable with Atari POKEY chip sounds. demo melody "Greensleeves" (2 note polyphonic with rhythm) jacks for microphone, headphone & AC- adapter