FIRST
RAP-2 - with SING-A-LONG		   strange squarewave Casio Rapman knock-off 

This apparent Medeli instrument from 1994 (?, serial sticker "94 04") was the Chinese answer to Casio Rapman RAP-1. Unlike the real thing, the main voice is squarewave (like MC-3) and there is no voice changer. Percussion employs short lo-fi samples of drumkit, scratch and voice sounds.

Like RAP-1, the spring loaded scratch disc is fake and only presses 2 buttons, but unlike it, disc and drumpads can be assigned to any of the 16 keyboard percussion samples. 12 of the 36 rhythms contain fixed-key accompaniments and reduce polyphony to 1, but unlike Rapman, with plain rhythms it stays polyphonic and the keyboard is longer, so it is hard to decide which is better.

This instrument was also released as Thompsonic TS-22 (seen on eBay).

main features:

eastereggs:

  • 12 lower note keys addable
  • metronome button addable (percussion test, button can cycle through all 16 samples)

    • notes:

    The rubber drumpad circle (button are plastic) and case design elements resemble Fujitone 6A. Preset sounds and rhythms are selected by typing 2 digit numbers; cipher and tempo buttons sound claves, which disturbs live performance. The demo starts talking "four, three, two, one", which was likely original planned for a lesson mode (like in Medeli MC-32) but not implemented. The combination of squarewave main voice with COB percussion sample IC resembles Elite MC2200 and Bontempi ES3000 (aka MC-2100). Despite instrument name "RAP-2" the CPU is "MC-RAP-1", so possibly the creator wanted to name the instrument "RAP-1" but feared trouble with Casio.

    The main voice sounds like MC-3 with very simple linear volume envelope (neither vibrato nor mandolin ring effects), which of course doesn't sound realistic. The 'guitar' doesn't decay and has 2s sustain. The 'j. organ' is percussive plain squarewave with 2s sustain; 'synth' is similar with thinner timbre. 'flute' is made from plain squarewave and resembles a clarinet. Fast played monophonic notes truncate others, which was possibly done to avoid note clusters in long sustaining sounds. Higher numbers than 31 (i.e. sound 12 = 'percussion') are ignored, but valid digits switch the sound.

    The percussion samples sound a little too high and are very short. So 'cowbell'  and 'claves' sound like short blips. 'scratch' 1..2 (used by scratch disc) are blatant copies of the corresponding Casio RAP-1 vocoder sounds, while 3 and 4 are a low and high hissy zap. The 'ha!' resembles a barking small dog or cuica, while the numbers are spoken by a male voice very short with truncated ends ("Yello"-style, "three" sounds like "freak"). Keyboard percussion sounds only on the rightmost 16 white keys; others stay silent.

    To assign percussion sounds to a drumpad or scratch disc direction, press "program" (LED lit). Hold the corresponding key and operate the pad or direction (you hear it sound). You can repeat this for others. Press "program" again (LED off) to end.

    The rhythms resemble Casio RAP-1 and were designed for oldschool rap. Also here those with accompaniment (like RAP-1) play fixed key and render the main voice monophonic, which makes them badly suited for melody play. The 3 note polyphonic accompaniment styles resemble the "Sonic the Hedgehog" videogame (funk or jazz patterns) and use a saxophone- like organ tone. Unlike RAP-1, at least those without accompaniment keep 4-note main voice polyphony.
     

    circuit bending details

    The First RAP-2 is build around the CPU "MC-RAP-1" (software variant of MC-3DX, crystal clocked @ 1MHz) with squarewave sound IC "DSG-MC-3" and sample percussion IC "RAP[?] 1203".
    RAP 1203 percussion sample IC scratch disc pushes 2 buttons
    This hardware strongly resembles Letron MC-3, but has an additional percussion IC and fewer LEDs. The high pitched button click is 'claves' played by the percussion IC. The unused percussion outputs of the DSG do nothing. The fake scratch disc only simulates 2 button presses.

    keyboard matrix

    The matrix layout is obviously based on MC-3, but the crippled software here has many features omitted. E.g. it supports no fingered nor single finger chord anymore, and the "program" button only assigns drumpad sounds instead of a custom drummer. Although output pin 37 still exists, its matrix places are all empty. The matrix out pins 34..37 also drive each a panel LED through a 2.7k resistor from +Vs; for this the pauses between the short scan pulses (when the inputs are active) are pulled lo to light the LED (else hi). Eastereggs are 12 lower note keys and a metronome-like percusion test mode.
     
    41
    40
    39
    38
    34
    35
    36
     
    CPU pin
    out 4
    out 3
    out 2
    out 1
    out 5
    out 6
    out 7
    out / in
     
    o
    B4
    o
    B3
    o
    B2
    o
    B1
    -
    tempo -
    -
    in 12
    4
    o
    A#4
    o
    A#3
    o
    A#2
    o
    A#1
    P.
    disc right
    tempo +
    -
    in 11
    3
    o
    A4
    o
    A3
    o
    A2
    o
    A1
    P.
    disc left
    demo
    -
    in 10
    2
    o
    G#4
    o
    G#3
    o
    G#2
    o
    G#1
    P.
    cowbell
    P.
    metronome
    -
    in 9
    1
    o
    G4
    o
    G3
    o
    G2
    o
    G1
    P.
    hihat
    -
    '4'
    in 8
    8
    o
    F#4
    o
    F#3
    o
    F#2
    o
    F#1
    P.
    base
    -
    '3'
    in 7
    7
    o
    F4
    o
    F3
    o
    F2
    o
    F1
    P.
    tom
    -
    '2'
    in 6
    6
    o
    E4
    o
    E3
    o
    E2
    o
    E1
    P.
    snare
    -
    '1'
    in 5
    5
    o
    D#4
    o
    D#3
    o
    D#2
    o
    D#1
    -
    -
    '5'
    in 4
    29
    o
    D4
    o
    D3
    o
    D2
    o
    D1
    P.
    program
    -
    '6'
    in 3
    28
    o
    C#4
    o
    C#3
    o
    C#2
    o
    C#1
     -
    start/stop
    rhythm
    select
    in 2
    27
    o
    C4
    o
    C3
    o
    C2
    o
    C1
    o
    C5
    -
    voice
    select
    in 1
    26

    The input lines are active-low, i.e. react on GND. Any functions can be triggered by a non- locking switch in series to a diode from one "in" to one "out" pin.
     

    legend:
    "o"
    		 = keyboard key
    P.
    		 = drumpad
    orange
    background     		 = easteregg (unconnected feature)

    • metronome
      A button at 1->35 starts a simple beat (like a metronome) using the 1st percussion sound. Pressing the button again cycles it through all 16 available percussion sounds. This was likely intended as a test mode for the percussion IC. Press "start/stop" to exit.

    pinout RAP 1203

    The "RAP[?] 1203" (11 pin COB, by Medeli?) is the percussion IC of First RAP-2. It is monophonic with on board clock source (capacitor + 2 resistors) and contains 16 low resolution percussion, scratch and voice samples {base, tom, snare, conga, hihat, cowbell, claves, scratch 1..4, "ha!", "one", "two", "three", "four"} selected by bit combinations on 5 data bus inputs. 2 additional handshake inputs indicate when the data is valid.

    This description was made from my own examination and likely inaccurate. All pin names were chosen by me.
     
    pin name purpose
    1 GND ground 0V
    2 D1 data bus in
    3 D2 data bus in
    4 D3 data bus in
    5 D4 data bus in
    6 D5 data bus in
    7 /SE1 handshake in 1
    8 /SE2 handshake in 2
    9 /RESET reset
    10 SND audio out
    11 +Vs supply voltage +5V (through 47 Ohm resistor)

    Shorting both handshake lines with each other double triggers some samples, which makes me conclude that they have to be pulled low and high again in a certain order (like the protocol of Casio 4 bit bus) to permit clock independent communication.
     
     removal of these screws voids warranty...    
    WarrantyVoid
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