realistic mg-1

REALISTIC MG-1 CONCERTMATE

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This is a pimpy little synth. It was sold through the Realistic electronics

chain, also known as Radio Shack (and as Tandy, in the UK at least). It was

relatively cheap but had a design from Moog Music (from after Robert Moog

had left?) including the patented ladder filter. It consisted of a monophonic

synth, dual oscillator, lfo, noise, filter, env, and a ring modulator. On top

of that there was an organ circuit to give 'polyphony'. It was not really

polyphonic although different descriptions will tell you it had 10 voices.

These write-ups are by people who probably only had 10 fingers, the truth is

that the organ circuit was as per any other - it had a master oscillator at

about 2MHz and this was divided using binary counters to deliver a frequency

for every note. The output of the 'poly' section was lamentable at best, it is

a fairly pure square wave passed through the filter and contour. This is fully

emulated although in addition to the contour bristol implements a per note

envelope just to groom the note - this prevents ticks when new keys are pressed

with the mono envelope fully open. There is no access to this env, it just has

fast attack and decay times to smooth the signal and is preconfigured by the

user interface on startup.

The mono section is reasonably fun, the oscillators can be synchronised and

there is a ring modulator so the range of sounds is quite wide. The emulator

uses a chaimberlain filter so is not as warm as the Moog ladder filters.

The list of people who used this is really quite amazing. The promotion for

the product had Elton John holding one up in the air, although seeing as he

probably already had every other synth known to man, holding it up in the

air is likely to be all he ever did with it. Who knows how much they had to

pay him to do it - the photo was nice though, from the days when Elton was

still bald and wearing ridiculously oversized specs.

Tuning:

One control each for the poly oscillator and mono oscillators

Glide:

Only affects the monophonic oscillators.

Modulation:

One LFO with rate and waveshape selection

produces tri, square and S/H signals.

can trigger the envelope

One noise source.

The modulation can be directed to:

Oscillators for vibrato

Filter for wah-wah effects

Oscillator-1:

Tri or square wave

Octave from -2 to 0 transposition

Sync selector (synchronises Osc-2 to Osc-1)

Oscillator-2:

Tri or pulse wave

Detune. This interoperates with the sync setting to alter harmonics

Octave from -1 to +1 transposition

Contour: This is not an ADSR, rather an AR envelope

Sustain: AR or ASR envelope selector.

Tracking: controls mono oscillators

Envelope control

Key tracking (gate, no env)

Continuous (always on)

Rise (attack time)

Fall (release time)

Filter:

Cutoff frequency

Emphasis

Contour depth

Keyboard tracking off, 1/2, full.

Mixer: Levels for

Mono Osc-1

Mono Osc-2

Noise

RingMod of the mono oscillators (called 'bell').

Poly Osc level.

Master Volume control.

One extra button was added to save the current settings. For the rest the

controls reflect the simplicity of the original. The implementation is a single

synth, however due to the engine architecture having a pre-operational routine,

a post-operational routine and an operate(polyphonic emulator) the emulation

executes the mono synth in the pre- and post- ops to be mono, these are called

just once per cycle. The poly synth is executed in the operate() code so is

polyphonic. This leads to one minor deviation from the original routing in

that if you select continuous tone controls then you will also hear one note

from the poly section. This is a minor issue as the poly oscillator can be

zeroed out in the mixer.

It is noted here that this emulation is just a freebie, the interface is kept

simple with no midi channel selection (start it with the -channel option and

it stays there) and no real memories (start it with the -load option and it

will stay on that memory location). There is an extra button on the front

panel (a mod?) and pressing it will save the current settings for next time

it is started. I could have done more, and will if people are interested, but

I built it since the current developments were a granular synth and it was

hard work getting my head around the grain/wave manipulations, so to give

myself a rest I put this together one weekend. The Rhodesbass and ARP AXXE

were done for similar reasons. I considered adding another mod button, to make

the mono section also truly polyphonic but that kind of detracts from the

original. Perhaps I should put together a Polymoog sometime that did kind of

work like that anyway.

This was perhaps a strange choice, however I like the way it highlights the

difference between monophonic, polyphonic and 'neopolyphonic' synthesised

organs (such as the polymoog). Its a fun synth as well, few people are likely

to every bother buying one as they cost more now than when they were produced

due to being collectable: for the few hundred dollars they would set you back

on eBay you can get a respectable polyphonic unit.

So here is an emulator, for free, for those who want to see how they worked.