Casio Rapman RAP-1, DJ-1 (RAP-2)

Casio DJ-1

RAP-1
digital children keyboard with voice changer

Casio RAP-1

This keyboard from 1991 (embossed case date) has many rap/ rock/ house rhythms and a weird sounding microphone voice pitch changer which can be used to feedback the own keyboard sounds through it as an effect.

But the scratch disc of this toy is fake (simulates 2 button presses), and also the 3 drumpads can be only switched between 2 fixed sound sets. Nothing can be assigned or programmed in any way. The main voice uses variants of SA series sounds. This is not a synth, but the voice changer can be used to distort them by pointing the microphone at the internal speakers to produce somewhat FM-like rough feedback noises.

This keyboard was also released as Realistic Rap-Master.

main features:

32 midsize keys
built-in speaker
polyphony 3 notes (only one note with rhythm :-( )
25 preset sounds {brass ens, echo brass, flute, synth-reed, synth-lead, piano, vibraphone, elec organ, wah voice, warm strings, elec bass, metal guitar, sitar, church bells, bells, percussion, gamelan, agogo, band hit/ brass hit, orchestra hit, vocoder, twinkle echo, car horn, ambulance, emergency alarm}
30 preset rhythms (partly with fixed- key accompaniment) {beat 1..12, rap 1..2, heavy rap, hip-hop 1..4, mellow rap, rock 1..2, funk 1..4, r?b, house 1..3}
voice changer with 5 position slider (pitch shift)
tempo +/- buttons
3 drum/effect pads + scratch disc controller mock-up (works just like 2 buttons) + mode button to switch between 2 fixed sound sets for these. {agogo, base, snare | orchestra hit, band hit, brass hit}
sound engine like Casio SA series instruments (crystal clocked).
multi-chip hardware:

CPU= "OKI M6521-06, IX2003" (60 pin SMD)
voice changer IC= "OKI M6322, 183034" (24 pin SMD)

jacks for phones, aux, microphone

eastereggs:

5 cipher buttons addable
3 drumpads addable (no new sounds)
rhythm select button addable (12 patterns)
percussion glitch modes (kind of keyboard drumkit, based on "any key play" and "melody guide")
The 2 short samples from both ends of the "scratch disc" can be played simultaneously without problems despite the mechanical design of the disc normally prevents this.
This instrument can make incredible noises by feeding its own sounds through the microphone back into the voice changer. The results are e. g. very eerie, droning, booming and disharmonious noises those can be compared best with the horror movie music that Oskar Sala composed on the instrument "Mixtur- Trautonium". Also somewhat acid- like tweeting can be produced. I plan to add a knob for internal direct feedback for this.
Voice changer likely can be rewired for finer pitch resolution (17 steps on +/- buttons).

modifications:

voltage regulator added, AC adapter jack polarity re-wired to standard.

notes:

The main voice is based on the SA series sound engine, but particularly percussion sounds and 'piano' differ. It is a pity that nothing can be reprogrammed in this instrument; some sounds (sitar, wah-voice etc.) are very nice.

The preset sounds are based on classic SA-series, but some are special. "echo brass" resembles the known "brass ens" with echo. "flute" is "whistle" with less reverb. "synth reed" is duller. "piano" resembles here "synth piano" (less percussive, Rhodes-like). "vibraphone" has here less sustain. "percussion" is {scratch 1?, scratch 2?, clave?, hihat}. "gamelan" sounds a semitone lower. "agogo" can be played melodic and resembles a toy piano. "band/brass hit" and "orchestra hit" are grainy lofi versions of a sound that was somewhat overused in that era (e.g. by Michael Jackson and in techno). "vocoder" is that granular sound from the scratch disc in decaying and looped with additional echo. The siren sounds "ambulance" and "emergency alarm" here have a chromatic key scaling and so can be played melodically.

The rhythm set differs from the usual SA-series. It is focussed on rap/ hip hop stuff, and some patterns contain fixed key accompaniment. To enable rhythm, the power switch has to be set to "rap" position, which makes the main voice monophonic. Operating any drumpad or scratch disc mutes rhythm for the rest of the bar. Like with most toy keyboards, the scratch disc is fake; it is spring loaded and does not more than pushing on 2 buttons (1 per direction).

The voice changer pitch-shifts the microphone input and has a grainy digital lo-fi timbre.

circuit bending details

The hardware contains a voice changer IC "OKI M6322" that is clocked by its own 4 MHz crystal and runs independently from the CPU "OKI M6521-06" (crystal clocked at 21.725 MHz).

Touching its crystal pins with metal crashes the cpu and often makes very interesting drum rhythm mess. I found no satisfying way yet to replace the crystal with anything controllable that has a wide enough frequency range for a good pitchbend, but modifications for this are planned. Also a shitshot by re-plugging the AC adapter can mess up the sounds in sometimes interesting ways.

The behaviour that the only 3 note polyphony is reduces to 1 when rhythm plays (no matter whether the selected rhythm makes use of the 2 occupied melodic voices) is a sign of very poor software design. The CPU type "OKI M6521" hints that it is a close relative of the Casio PT-88 hardware with changed internal ROM, which makes me conclude that the "rap" mode is genuinely nothing else than the PT-88 "auto play" mode that without connected ROM-Pack uses the internal SongBank memory, which here contains instead of songs 30 endless loops as preset rhythms. Only the "demo" (i.e. cycle through all songs) on the last key seems to be disabled. Because 3 polyphony channels are statically assigned to ROM-Pack playback, only 1 remains for the main voice. Also that hitting any drumpad mutes the rhythm track for 1 bar perfectly matches PT-88 behaviour.

keyboard matrix

The Rapman RAP-1 is obviously derived from Casio PT-88 hardware, so the layout is very similar. 5 cipher buttons, 3 drumpads, glitchy "melody guide" variants and 2-note polyphony mode can be added.

This matrix was analyzed by myself with the help of service manuals of Casio ML-2, ML-3, ML-1.

31 KI0 32 KI1 33 KI2 34 KI3 35 KI4 36 KI5 37 KI6 38 KI7 CPU pin

in 0 in 1 in 2 in 3 in 4 in 5 in 6 in 7 in / out

o
F3 o
F#3 o
G3 o
G#3 o
A3 o
A#3 o
B3 o
C4 out 0 39 KO0

o
C#4 o
D4 o
D#4 o
E4 o
F4 o
F#4 o
G4 o
G#4 out 1 40 KO1

o
A4 o
A#4 o
B4 o
C5 o
C#5 o
D5 o
D#5 o
E5 out 2 41 KO2

o
F5 o
F#5 o
G5 o
G#5 o
A5 o
A#5 o
B5 o
C6 out 3 42 KO3

P.
1 (brass hit) P.
2 (band hit) P.
3 (orchestra hit) P.
4 (scratch lo) P.
5 (scratch hi) P.
6 (rimshot) P.
7 (base) P.
8 (snare) out 4 43 KO4

N.
'1' [0] N.
[1] N.
[2] N.
'2' [3] N.
[4] stop tempo
- stop out 5 44 KO5

N.
'3' [5] N.
[6] N.
[7] N.
'4' [8] N.
'5' [9] P.
variation R.
select tempo
+ out 6 45 KO6

M.
melody guide M.
melody guide 2 M.
melody guide 2 M.
melody guide M.
any key M.
rap M.
play polyphony 3
[diode] out 7 46 KO7

The input lines are active- high, i.e. react on +Vs, thus any functions are triggered by a switch in series to a diode from one "out" to one "in" pin.

legend:

"o" = keyboard key

R. = rhythm

N. = number entry (cipher buttons)

P. = drum-/effect pad, scratch disc

M. = mode select switch

orange
background = easteregg (unconnected feature)

grey
background = unconnected doublet

The LED matrix pins LY# and LX# are not used in this instrument, but they still seem to work like in PT-88. On oscilloscope there is much activity particularly in "rap" mode before selecting a rhythm. The PT-88 in this situation shows a walking light running from left to right.

eastereggs

5 additional cipher buttons can be added (corresponding PT-88 ciphers are in "[ ]") to select more sounds, but many cipher combinations (often with KI2) are mute.

3 additional drumpad buttons at KO4->KI5..KI7 play rimshot, base, snare. But these are anyway reachable through the pad variation button and nothing special. In variation mode the pad at KO4->KI5 sounds "echo brass" and the other 2 stay mute.

The "rap" mode of RAP-1 technically corresponds to "auto play" of PT-88. So the rhythms and fixed-key accompaniments are actually internal songs those repeat in a loop. The other keylighting stuff exists too, but behaves glitchy. The "melody guide 2" (without waiting) seems to be just like "rap". The "any key" mode waits on key presses to step through patterns, but behaves very glitchy. It is in a kind of keyboard drumkit mode that plays on each key a different percussion or short synth sound, but depending on the pattern, some keys sound only when pressed multiple times. The rightmode key ("demo") starts the first rhythm in normal mode (like "rap"; you can exit with "stop"). The "melody guide" seems to do the same. (I didn't examine details.)

In RAP-1 there is a fixed diode soldered at KO7->KI7 (located near the "tempo -" button) that enables its 3-note polyphony. It is only sensed during power-on (see PT-88), and removing it reduces polyphony to 2 notes. It is unknown why the polyphony isn't 6 notes; possibly Rapman for each channel layers 2 internal subvoices to sound thicker, or occupies more CPU capacity for higher sample playback resolution.

shitshot

Touching clock pins makes all kinds of bizarre crash noises. Also a shitshot on the power supply line (e.g. simply by battery wiggling) works. My RAP-1 needs 1 second without power to fully reset (which may be also result of my voltage regulator stuff), which makes it particularly sensitive to such tricks.

pinout M6322

The "OKI M6322" (24 pin SMD) is the voice changer IC of Casio Rapman and DJ-1. The documented IC (datasheet OKI MSM6322) contains an 8-bit ADC and 9-bit DAC and is clocked with 4MHz. Speech pitch can be adjusted in 17 steps by 1 octave down or up. It has an internal microphone preamp. The preamp and filter pins need external discrete components.

Most interesting is that pitch control in 17 steps is much finer than the 5 step slide switch used in these instruments. The IC can be wired to either use a 4-bit combination (e.g. locking switch contacts) or simply 2 buttons (up/down) for pitch select. The mode is set by wiring pin 6 hi or lo.

pin name purpose

1 UP.C (P2) pitch up button in | pitch switch bit 2

2 DW.C (P1) pitch down button in | pitch switch bit 1

3 PD (P3) power down in | pitch switch bit 3 (MSB)

4 STB /ACT standby in | chip select

5 PRST (P0) reset (sets pitch to 8) | pitch switch bit 0

6 MS mode select in: wired lo=up/down buttons, hi=4-bit (e.g. locking switch)

7 TEST1 (wired to ground 0V)

8 TEST2 (wired to ground 0V)

9 DA0 dac audio out (unfiltered)

10 FIN2 internal filter audio in

11 AOUT audio out (through internal filter)

12 AVDD analogue supply voltage +5V

13 FIN1 amplitude control out

14 LIN audio line in

15 LOUT microphone preamp out

16 MICIN microphone in (through capacitor)

17 SGC reference voltage in (half AVDD)

18 AGND analogue ground 0V

19 SG reference voltage in (half AVDD)

20 N.C. -

21 DGND ground 0V

22 XT crystal in (4 MHz)

23 /XT crystal out

24 DVDD supply voltage +5V

In the Rapman series Casio also released a boring belt- mountable rhythm/ scratch sound toy without voice changer named RAP-10. A much bulkier Rapman-like keyboard (with cassette recorder) was Rap Studio RAP-2 that is better known as Casio DJ-1. A blatant RAP-1 knockoff was the First RAP-2 (similar case and accompaniment, no voice changer, squarewave sound + short rap/ percussion samples).

Casio DJ-1

This rare keyboard of 1992 (embossed case date) is not an exciting forgotten DJ instrument by Casio. It is not a lost Voice Arranger. It is just an overly bulky boring toy tablehooter with 2 fake scratch discs, very similar like Rapman RAP-1.

The 6 drumpads play each exactly one sound (3 are speech samples) and the right scratch disc just pushes on 2 buttons those play the same scratch sample at 2 speeds. The left disc is only a big knob to change pitch (playback speed) of those pads and right disc. Mildly interesting is that the built-in cassette recorder has a tempo knob and (like a reel tape recorder) can select both stereo channels individually or together like a primitive 2-track recorder. The keyboard has variants of SA series sounds and various rhythms (mostly hiphop, some with fixed-key accompaniment). Like Rapman it has a voice changer (5 pitches), which most interesting use case is to distort internal sounds by pointing the microphone at the internal speakers to produce somewhat FM-like rough feedback noises.

This instrument was also released as Casio Rap Studio RAP-2.

different main features:

2 built-in speakers (of reasonable quality)
25 preset sounds {vocoder, echo brass, brass ens, synth reed, synth lead, flute, piano, elec organ, vibraphone, warm strings, elec bass, metal guitar, bells, church bell, drum set, percussion, gamelan, agogo, band/ brass hit, orchestra hit, waw voice, twinkle echo, car horn, ambulance, emergency alarm}
30 preset rhythms (partly with fixed- key accompaniment) {M-O-R, one-four plus, hip-hop e, DJ, mellow rap Eb, groove 1..12, dee-flat, one-four, heavy thang, hip-hop D, hip-hop B, house rock, downtown, mellow rap Bb, funky D, funky A, S-bad, homey, J.B.E.} (selected through keys)
volume sliders for main, inst., mic
6 drum/effect pads {slap bass, e-guitar chord, "Come on ya!", "Uhh", "Gimme a beat!", whoosh!}
2 fake scratch discs (right simulates 2 drumpad buttons with a scratch sample | left = pitch knob (>1 octave) for pads and right disc)
cassette recorder with channel selector {L, stereo, R} and tempo knob
multi-chip hardware:

CPU= "OKI M6521-09, 252006, Japan" (60 pin SMD)
effect pads sound IC= "OKI M6373-342, 233501, Japan" (18 pin DIL)
voice changer IC= "OKI M6322, IY3002, Japan" (24 pin SMD)

jacks for phones, aux, microphone

eastereggs:

8 drum-/effect pads with variation button addable.
rest see RAP-1

notes:

I really don't understand what Casio had in mind when making this bulky boring thing. With optimized software this could have become a fairly nice lofi groovebox (perhaps even saving data on cassettes like Casio KX-101), but with its unassignable pads and useless fake scratch discs Casio missed the change of building something exciting. At least they should have kept the full 100 preset sounds this CPU can handle. But remember that in the era of cheap ghettoblasters plenty of bulky plastic lofi trash with cassette drives was made and sold well. The case style with slanted speaker grills and green preset lists is untypical for Casio and was obviously imitating Yamaha instruments of its era. The case bottom is in a very strange violet hue which spectrum my digicam Samsung WB210 can not see. It renders it just grey like the top, so I had to retouch it (original example see left part of this). My old Jenoptik JD 4.1 x z3 digicam (which is oversensitive to violet) detected the difference without problem.

The preset sounds are based on classic SA-series, but some are special. The sound set is almost like Rapman RAP-1, but in different order. It powers on with "vocoder" instead of "brass ens", and canceling the last musical reference to hippie era, instead of "sitar" it got a 2nd drumkit "drum set" (several pitches of {base, tinny toy drum (timbales?), shaker 1, shaker 2}). Unfortunately nothing can be assigned to pads or scratch disc, which is also caused by bad hardware design, because to implement pitch control (left scratch disc), pads and right scratch disc are handled inside a self-contained sound IC that is too primitive to communicate with the rest.

Like in RAP-1, the rhythm set is focussed on rap/ hip hop stuff, and some patterns contain fixed key accompaniment. To enable rhythm, the power switch has to be set to "pattern" position, which makes the main voice monophonic. Operating any drumpad or scratch disc mutes rhythm for the rest of the bar.

The 6 effect pads and each direction of the right scratch disc trigger each a preset sample sound. Holding it retriggers the sound. The left scratch disc changes the pitch.

hardware details

The Casio DJ-1 is built around the CPU "OKI M6521-09" (crystal clocked at 21.725 MHz). But drumpads and right scratch disc are handled by a selfcontained sound IC "OKI M6373-342" that has no digital connection with the rest. Its clock rate is controlled by the potentiometer of the left scratch disc. Also the voice changer IC "OKI M6322" is clocked by its own 4 MHz crystal and runs independently.

The case bottom violet is invisible to my digicam. The side view photo is unretouched.

The hardware is fairly complicated with much cable mess inside, but most of the analogue section is occupied by the cassette recorder. To reach the main voice CPU, only unscrew the left PCB; you don't need to dismantle the rest. If you need to flip or remove the center (analogue) PCB, the cassette drive cables are too short. But you can unscrew its leaf switch ("play" contact) and unplug the tape head cable on PCB without desoldering.

The drumpads IC OKI M6373 was used in a similar way in Casio PA-31.

keyboard matrix

The keyboard matrix is identical with RAP-1 (see there) and so has the same eastereggs.

While the DJ-1 effect pads and scratch disc are not connected to the CPU at all, as eastereggs you can still find from RAP-1 the native 3 drum-/-effect pads, fake scratch disc and 3 inofficial drumpads with variation button.

2 of their percussion sounds differ. In variation mode and inofficial drumpads instead of rimshot there is a tinny toy drum (or timbales?). The cowbell has been replaced with a much duller and weaker variant (like muffling a cowbell with hands); I am not sure if this shall be a woodblock (it's still rather metallic), bongo or just a residue by replaced internal waveforms. The sound is not part of the 2 keyboard drumkit modes.

pinout M6373

The "OKI M6373-xxx" (18 pin SMD, xxx = software number of internal ROM) is originally a documented mask rom speech synthesizer IC (datasheet "OKI MSM6375/4/3/2-XXX"), that was used in Casio toy-like instruments to play preset samples on drumpads and fake scratch disc. It uses 4-bit ADPCM and has a built-in 12-bit DAC. It can be controlled by a host CPU through a digital protocoll or run standalone ("SW interface", e.g. when wired to drumpads). In CPU mode it can work 2-note polyphonic and has volume control, and additionally it contains a beep tone generator (8 tones,4 durations). But these features are likely controlled by internal ROM and can not be accessed externally. The 3 clock pins can be wired in different way, depending on use of a crystal or RC oscillator. Of this IC exist variants with different ROM size and with 24 pins.

M6375-xxx = 1 Mbit
M6374-xxx = 512 Kbit
M6373-xxx = 256 Kbit
M6372-xxx = 128 Kbit

18 pin 24 pin name purpose

1 13 I4 data in | switch in

2 14 I5 data in | switch in

3 15 I6 data in | switch in

4 16 /2CH 2-channel or echo mode in

5 17 /RESET reset

18 NC

19 NC

6 20 /BUSY/NAR busy or ST valid out

21 NC

7 22 SG filter capacitor out (1uF)

8 23 AOUT audio out

9 24 GND ground

10 1 VDD supply voltage 5V

11 2 OSC1 crystal in | clock RC resistor in

12 3 OSC2 crystal out | clock RC resistor out

4 NC

13 5 OSC3 /CS RC clock capacitor in | ST pin enable in

6 NC

7 NC

14 8 /ST data enable in

15 9 I0 data in | switch in

16 10 I1 data in | switch in

17 11 I2 data in | switch in

18 12 I3 data in | switch in

If you enjoy these keyboards voice changer, also look out for the great Casio VA-10, which is a synth-like small home keyboard with digital effect processor for the internal keyboard sounds and monophonic microphone input (stereo reverbs, pseudo- vocoder and much other strange digital stuff). The sound quality is not really better than Rapman, but way more versatile and polyphonic.

*removal of these screws voids warranty...*

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