Playskool - Kid Keys PS-635

Playskool - Kid Keys PS-635 (squarewave keyboard with POKEY percussion)

This monophonic toy keyboard from 1993 has nice POKEY rhythm and many sound similarities with the great Hing Hon EK-001. Unfortunately only 3 rhythms can be selected by hand, despite its demo tunes contain many additional rhythms.

main features:

29 mini keys
monophonic main voice
4 OBS preset sounds {violin, flute, piano, organ} (selected by a slide switch)
3 OBS preset rhythms with unique percussion
volume knob
tempo +/- buttons (16 steps)
sound generation is based on multipulse squarewave and resembles much the Hing Hon EK-001. 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. They all use digital envelopes and either squarewave or shift register noise. The cowbell (squarewave with digital envelope and zipper noise) sounds like a bottle hit. The snare uses a very rough and impulsive hissing shift- register noise (like a historical videogame's MG shot), the hihat uses a quieter hiss. The base is just a quick fading squarewave. These percussion in spite of their basslessness sound incredible vigorous and are an as outstanding sound discovery as the nowadays so well known and everywhere imitated TR-909 base drum.
primitive sequencer (record/ playback, no edit, stores 62 notes)
12 demo melodies (monophonic monotos with each a different rhythm)
headphone jack

eastereggs:

When the sound select switch is set into intermediate positions, the CPU switches quickly between the selected sounds, resulting in a rough and buzzy kind of fast arpeggiator effect (like known from C64 SID musics).

notes:

The key colours of this instrument look like imitated from the Casio EP-20. The PS-635 has basically the same exceptional POKEY sounds like the great Hing Hon EK-001 (see there), and by its behaviour the CPU seems to be indeed a variant of it; e.g. selecting multiple preset sound lines simultaneously results in the same buzzy arpeggiator timbres. Unfortunately in opposite to the EK-001 only 3 preset rhythms and 4 preset sounds can be selected, which limits its use a lot.

The 12 demo tunes use many additions rhythms, thus it may be possible to enable these also for manual play as keyboard matrix eastereggs. Likely it is at least easily possible to add a switch or potentiometer to disable the main voice during the demos to use their rhythm track as a drum machine. (I haven't analyzed the hardware closer yet.)

The 12 demo melodies are simple monophonic monotos (sound loops) those employ the currently selected main voice sound but each of them has its own rhythm. The demos are:

Happy Birthday
London Bridge is Falling Down
Oh Susanna
Mary Had a Little Lamb
Silent Night
Jingle Bells
Twinkle Twinkle Little Star
For Elise
In a Persian Market
Home Sweet Home
La Cucaracha
Santa Lucia

Don't be confused if anybody tells you that this instrument would have somewhere a "music card slot"...

On the case top there is indeed a small rectangular hole labelled this way and in the case bottom is a compartment for musical score cards of cardboard. My used specimen came with these five cards:

Happy Birthday
Oh Susanna
Silent Night
Jingle Bells
In a Persian Market

These score cards can be inserted with their protruding end into this slot (which holds them in a very wacky and fragile way), but this will not affect in any way the electronic operation of this instrument. They are in no way anything sophisticated like ROM cartridges but only note sheets and these wacky cards are even almost impossible to remove from their compartment without folding them badly or even accidentally tearing them. (One of mine came already torn.)

The sequencer is a similarly banal thing like with My Music Center, but in opposite to the latter this one is always recording the notes you play (until the memory is full, but no pauses), and it does not loose its contents unless "clear" is pressed. Even powering off into standby mode (it has a button instead of a power switch) does not clear the memory contents. The playback speed can not be changed with the tempo controls.

circuit bending details

Nick Santos sent me an e-mail with the following hardware tips about the Playskool PS-635:

"Although I am still in the experimentation and documentation stage of this bend I have found some promising bends. As you may have noticed, pins 10-26 seem to deal with they keys and buttons of this device. I saw that pins 10 and 12 were being used but pin 11 was conspicuously unused, I used some wire and probes and proceeded to connect pin 11 to the other key control pins with pleasing results pin 11 connected to pin 15, 16 17 or 18 will produce the kick, cowbell, loud snare and soft snare respectively. When pin 11 is connected to pins 21-26 it will produce lower pitch notes that were not included in the design. You mentioned that you would like to use the pre programmed rhythms and cancel out the main instrument voice, I have discovered how to do this as well. Connect the pin nearest the headphone jack of the capacitor nearest the headphone jack, to pin 1 of the instruments main chip, this will completely cut out the main voice and leave the rhythm (if you attach to the wrong pole of the capacitor a very faint main voice will remain) to do the opposite and strip away the rhythm from the songs connect the same pin of the capacitor to pins 5 or 6 of the main chip (it will also boost the volume).
...
I hope this helps you and helps other people who wish to bend this instrument as well."

Attention: I haven't verified this info yet.

A much better instrument with the same sound style is the Hing Hon EK-001. Another monophonic instrument with multiple demos and this sound hardware is the Yongmei MS-210B. (Sorry, I initially confused its name with a wrong keyboard.) Someone e-mailed me that another close variant was the Kiddesign - Barbie Music Center BE-630.

*removal of these screws voids warranty...*

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