Mega - My Music Center

My specimen has the brand name Mega, but also other versions may exist. In the year 2000 on Asian Sources the Hong Kong company Hundred Power Industries Limited offered this tablehooter with the internal name HP-98. (The 98 may hint to the initial release year.) My Music Center is one of the most widespread toy keyboards ever made, and it was also released in a zillion of other, partly very different looking case variants. In late 1990th there even was a time when about 2/3 of all toy keyboards with rhythm on the market contained exactly this hardware. The sound hardware of My Music Center nowadays has set the base of a large hardware family of other complex toy keyboards those often have more features or less flaws, but many of these have other restrictions or boring sounds, thus the original is still interesting.

main features:

• 32 mini keys
• built-in small speaker (sounds thin and distorting)
• theoretically 2 note polyphony, but a chip bug randomly cuts the tone of a held down key when a 2nd is pressed =>only monophonic play is reliably possible.
• 8 OBS preset sounds {piano, organ, violin, trumpet, mandolin, bell, music box, guitar}
• 8 OBS preset rhythms {slowrock, rock, new new, disco, march, waltz, samba, blues} (no accompaniment, with rhythm only monophonic play)
• volume +/- buttons (8 steps)
• tempo +/- buttons (22 steps)
• 4 drumpad + select button to switch them between drum or animal samples {base, snare, hihat, cymbal | dog, frog, duck, bird}
• The 4 channel sound generator synthesizes each main voice sound by layering 2 waveforms those have a digitally switched volume envelope (with well audible ticking  zipper noise). The envelopes are rather linear than logarithmic and thus end too soon. The waveforms on both channels are detuned to create a chorus effect. In the demo tunes the 2 subvoices of each main voice sound are split to permit the sound generator to play 4 note polyphonic musics (without chorus). Percussion and effect samples share the same 4 channels.
• percussion = boring low- res drum samples {base, snare, hihat, cymbal}
• The CPU contains a 1 bit pulse width modulation D/ A converter which outputted sequences of on/ off pulses get turned into analogue wave forms by a capacitor. This sample output frequency intermodulates higher notes and gives them an unusual glassy timbre.
• CPU "INOVUS  IA 371  PCB952" (22 pin COB module) with DC voltage controllable clock oscillator
• simple sequencer (monophonic record/ playback of 38 notes or drum pad events, no edit, quite useless because contents is erased as soon anything else but "play" is pressed).
• auto power- off
• 6 wonderful orchestrated polyphonic demo melodies

Here you see the pitchbend controls and speaker mute switch added by me.

modifications:

• cinch sound output, speaker mute switch and AC adapter jack with regulator added.
• treble pot added.
• pull down resistors added to the keyboard matrix input lines to prevent unreliable keyboard function when batteries are empty.
• handmade pitchbend wheel (without spring) and 2 clock speed preset pots added between those a yellow button above the wheel switches back and forward. The 1st pot (for released button) is in series to the pitchbend one, the 2nd (for pressed button) is not connected to it; though the 2nd pot can e. g. be adjusted to a fixed frequency near crashing which makes many weird shitshot sounds when holding keys and pressing the button.

notes:

Attention:  There are multiple different My Music Center versions with almost the same case but different CPU and thus different sounds and demos. E.g. there is one with the sound hardware of Musical Centre, which has different sound and rhythm names. The original (and most widespread?) My Music Center that I described here plays no start-up jingle after power on and button presses play without rhythm a quiet hihat noise while most others play a short beep or with OBS preset sound buttons the corresponding sound.

All preset sounds have a volume envelope with well audible ticking  zipper noise and contain a chorus effect with slow tremolo. They all have short sustain, thus no very short blipping notes can be played, but great is that the sounds of My Music Center (and most of its variants) can be time dynamically played, i.e. in preset sounds with slow (non- percussive) attack you can play quieter notes by pressing a key very short, because this prevents the attack phase to reach full volume and instead directly goes into the release phase, which makes the sustain of the note start at lower volume. Especially the "trumpet", "guitar" and "music box" sound very unique, harsh and digitallic. Especially the high notes of the "trumpet" have very strong DAC aliasing noises those produce disharmonic overtones similar like a ring modulator. The "guitar" sounds like a cross between sitar and banjo and has a very strange and buzzy, wire- like roaring bass range. The "mandolin" rings with 8Hz and the percussive attack changes its timbre in a strange way, which makes the sound very unique; when 2 notes play simultaneously, the ring of both voices can have different phases. The "bell" is rather a vibraphone and the "organ" is more a harsh accordion; "violin" is similar but duller and has slow attack. The piano in the opposite sounds even more realistic (although honkytonk- like) than the one of many early non- toy keyboards. The "music box" is particularly great for new age style musics.

Interesting for live play tricks is that the 8 OBS preset sound buttons can also be pressed while keys are held down without stopping their notes. By rhythmically pressing these buttons, this way many strange effects can be created; especially switching to "mandolin" adds the mandolin ringing to the timbre of a currently held note, or switching from "mandolin" to something else quits the ringing. Other changes only affect new notes, this way 2 simultaneous notes with different timbre can be played by holding a key, switching the sound and then pressing a 2nd key. Sometimes this messes up the keyboard in strange ways that some keys keep a different timbre until some other notes are played. Generally the original My Music Center has lots of bizarre sound glitches those make the behaviour a bit unpredictable. The most annoying one is the polyphony bug, which semi- randomly makes a new note truncate a held or still sounding one, which makes polyphonic play almost impossible. (If you don't like this, buy a variant with My Song Maker hardware, which works much better.) During a sustaining preset sound (e.g. "violin") trilling a key a few times sometimes makes the note get stuck and keep playing for 3 seconds; then it stops with a sudden end click. Sometimes a played note randomly lacks the 2nd suboscillator (i.e. no chorus). Most button presses (e.g. sound select buttons) play a closed hihat noise that may disturb during live play, but this noise doesn't occur so far any sound or rhythm is still playing.

The only 4 percussion sounds are boring dull and noisy hissing low- res samples without dynamics. The rhythm patterns are partly quite long but nothing spectacular. But at least the 4 drumpad buttons can be switched to animal voices, those growl nicely when pitched down by an added pitchbend potentiometer.

When turning the clock speed very low, the pulses from the 1 bit D/A converter get audible and add more and more bizarre spectral harmonics to the down pitched sounds the lower it gets turned, until the sounds turn into series of short bursts of rhythmical bleeps those slowly change their structure. This fascinating effect doesn't exist in normal downsampling algorithms of PC programs etc. because it stems from the 1 bit D/A converter. Due to in this mode the keyboard reacts way too slow for playing, the 2nd clock pot can be set to a normal speed to make the IC recognize key presses by quickly pressing the yellow button each time a key is changed.
 

Also the animal voices sound very bizarre and alien- like when pitched down due to the additional harmonics. With the pitch wheel they can even be a sort of "record scratched" slow and fast; the frog e. g. turns into a kind of heart beat and the duck into an alien burp when messing around with them. This is very interesting for making a little sinister and dense sounding slow ambient musics. Shitshooting the program by overclocking often results in strange keyboard sounds (e. g. hissy noises) and especially the demo melodies start to play with changed instrumentation (e. g. the PCM drum or animal samples as their main voice - a hardware feature that is never used by the normal operation). The added cinch output jack sounds a little muffled by too much bass =>a high pass filter may help.

The monophonic record/ playback sequencer is quite useless because it looses its contents when anything but "re-play" is pressed. (Playing notes or drumpads delete and overwrite the sequence.) At least it records also drumpad events and you can immediately restart the sequence (make it rhythmically stutter) by pressing "re-play" again. You can also during playback switch the preset sound, the tempo and the mode of the recorded drumpad events (drums or animal), but that's all.

The 6 demo melodies of this instrument are:

1. Jingle Bells
2. Spain Coffee
3. Santa Claus is Coming Down to Town
4. Song of Spring
5. La Primavera
6. Let It Be

Superb Sound - EK-91DX

(photo from eBay, showing my specimen)

Yes, although it doesn't look so, even this small blue 29 mini- keys tablehooter with its bombastic high- end hifi style logo "SUPERB SOUND - AUDIO PRODUCTS" is indeed based on the original 1st generation My Music Center CPU. Despite this thing features a real 6V power supply jack, it is certainly the absolutely lousiest variant around, because this little squeakbox is so mutilated that everything besides 4 sounds {piano, violin, bell, music box}, 5 rhythms {rock, disco, march, samba, blues}, tempo +/-, the demo button (6 great melodies) and the sequencer was omitted. Instead of the volume +/- buttons it contains a 5 step slide switch (0=mute, thus only 4 steps function), but even at the lowest level it yells so loud and harsh that you fear to get tinitus, and you can always hear the keyboard matrix buzz with constant volume. Even more weird, this thing is only monophonic, and this not because the CPU has no 2nd voice, but simply because the OBS sound buttons were replaced by a 4 step slide switch, which simulates a continuously held down button and thus blocks the keyboard matrix. I really can't imagine why the manufacturer did this; likely its case was initially designed for a different sound hardware (corresponding to the switch layout), and later either the original chip was not available anymore or the manufacturer wanted to make a cheaper or more modern(?) sounding version by mutilating My Music Center circuitry. However, this tablehooter is really crap, and unless you intend to become deaf or make the mankind cry for earwax, don't buy one. There are much better variants of My Music Center around. (Outside the Yongmei hardware class (e.g. Golden Camel 7A), the EK-91DX is definitely a leading candidate in the ranking for the worst keyboards of the world.)

eastereggs:

• When the "tone select" switch is moved exactly between 2 sounds, the keyboard matrix blockade is removed, thus you can play 2 note polyphonic again (but with the same flaws like the original 1st generation My Music Center).
• As you may imagine, all function of the original My Music Center are likely still present in the keyboard matrix of the CPU, and thus this squeakbox could be theoretically upgraded with all missing functions of the original. But in reality this is not worth the afford since original My Music Center keyboards are still available very cheap and in large quantities on eBay.

Electronic Musical Keyboard 98289

It has only each 4 OBS preset sounds and rhythms and no drumpads. I don't know the manufacturer of this thing; on the white package box stands instead of a brand name only "CODE: 98289" and in French the following address:
 

Importateur: EUROPRO S.A RUE ST. BERNARD 73 1060 BRUSSELS BELGIUM FABRIQUE EN CHINE.

different main features:

• 29 small keys (almost midsize)
• only 4 OBS preset sounds {bell, violin, organ, piano}
• only 4 OBS preset rhythms {march, waltz, samba, blues}
• no drumpads
• volume slide switch (4 steps)
• CPU "TMP-3C, 2" (24 narrow pin COB)
• transistorized power amplifier (distorts badly)
• jacks for AC- adapter & headphone

RJP - Dynamic Keyboard MU-7986

The box shows the brand name StarMate and the keyboard photo on it has "PITCH" and "VOLUME" embossed below the fake wheels, while the keyboard itself lacks the writing and only has the brand name RJP (the company that created the wonderful Ramasio 892). Very bizarre is that my specimen came with 4 different looking instruction sheets (English, German, French, Spanish) of those the German and Spanish versions describe a totally different keyboard which the German sheet calls "Dynamische Tastatur MU-798". I was fooled by an eBay vendor who sold the MU-7986 to me and only listed the wrong and more professional features from that German manual.

Likely a predecessor of these was the simple toy keyboard RJP 896 Programmable Guitar Organ (same guitar- shaped case style but only 2 monophonic sounds, pitchbend, vibrato, 10 demos, no rhythm).
 

In the My Music Center hardware family many other instruments have been released with differently programmed sounds, behaviour and partly even higher resolution envelopes and timbres. The likely most complex instrument based on the classic 4 channel My Music Center sound generator is the Medeli MC-32 (49 midsize keys). Particularly interesting are also the bizarre Jin Xin Toys JX-20165 (with 36 sound variants) and the unique Potex - Super Jam (with 128 sound variants, 48 keys, slightly different timbre and warmer bass) and even a keyboard with simple synthesizer (i.e. thousands of sound variants!), perfectly responding keys and MIDI- out was released as Elta KE-491. A more versatile high fidelity successor of the My Music Center sound generator was used in the big fullsize keyboard Yongmei YM-2100 (with each 100 preset sounds & rhythms, nice fingered accompaniment).
 

removal of these screws voids warranty...
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