ELTA Solar 42 Emulator v2 and challenge

Edit: After reading this post, see here for the improved emulator version 2 and challenge

I was intrigued by Omri’s “ultimate drone machine setup” video in which he builds an emulation of the ELTA Solar 42. I am a sucker for a good ambient drone scape, so I decided to take a stab at creating my own emulator that more closely matches the sonic capabilities, workflow, and limitations of the hardware. Not exactly an easy task because the Solar 42 manual leaves out a lot of implementation and behavior details, and I could not find many reviews of the actual hardware.

Here are the only two videos I found that do any type of hardware walkthrough, and I think they both leave out a lot of details.

Never-the-less, I think I have come up with a decent emulation of all 8 voices, the stereo mixer, the sequencer, the LFOs, and the filters. I also laid out the Patch Master user interface to be similar to the hardware, and I include a patch bay with all the inputs and outputs. The UI and patch bay are completely isolated from the actual guts of the patch, so it should be easy to work with.

I opted not to attempt any emulation of the joystick, momentary drone buttons, piezo mic and envelope follower, or the touch plate keyboard with its many capabilities. You can patch in some of those capabilities via additional modules and the patch bay. Better yet, include your favorite MIDI controllers.

The patch includes documentation that breaks down all the differences between the emulator and hardware in more detail.

While building the emulator I decided to use as much Venom plugin as I could as long as it didn’t complicate things unnecessarily.

Here is a demo patch and video using the emulator. The Solar 42 is designed to be “played”. But this demo patch is fully auto-generative. In order to randomly fade in/out the 6 drone voices, I added some Bernoulli Switches that aren’t part of the emulator, but then, that is what the patch bay is for.

Solar 42.vcv (56.8 KB)

Updated version 1.1 with a bug fix is here.

I won’t hold my breath, but I would love to see what others can do with the patch.


About 30 minutes in, Brilliant!!

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Very nice. Reminds me of Sagan’s Cosmos series drones. I like it.

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And Vangelis, I should add. I have not thought of this in years, but the 1980 Cosmos Vangelis music must have had a big impact on me. I was 7 years into modular synths at that time, but in 1980 when I got my Apple II+ computer, I started doing digital music in 6502 assembler and interfaced with a hacked Casio keyboard and connected to my PAIA modular keyboard. In 1983 I moved to IBM PC compatible and started building MIDI interface boards. In 1985 I bought my Roland alpha-Juno2 and an Ensoniq Mirage digital sampler and player and bought a commercial MIDI interface board and in 1988 I began developing Meander. And, in my commercial music of the time, did a lot of generative drone music, inspired by Vangelis.

Anyway, you triggered a cosmic journey through time here :grinning:

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I was modifying you drone patch and started hearing pops and clicks, so I checked the CPU usage for your patch:


That was with 2 threads. With 6 I get:


So, I can continue playing with your patch. Others may want to do the same. This appears to be due to the number of modules rather than any one or few consuming excessive CPU usage.

Since this is such a complex patch, I will ask if anything can be said about the drone note pitch target or range? I see a C5 REFTONE module and I was guessing a C tone by ear. Is that correct?

Nice! Those comparisons are high honors. Thanks!

Yeah, definitely computer dependent.

On my PC I typically run with 2 or 3 threads. In this case I happened to be set at 3 threads, and I got ~55% avg 75% max as long as I wasn’t recording. When recording the max would often spike to 150+ and I would get live pops, but the recording is clean.

I just checked, and on my PC the sweet spot is 4 threads, giving ~50% avg, 60% max.

On my M1 MacBook Air everything hums along beautifully with 1 thread. Rack x64 yields ~50% avg, 52% max, and Rack ARM yields ~38% avg, 42% max

That REFTONE is a red herring. I just needed a controller that would give me integral values between 2 and 5 to control the number of sequencer steps, and that was the first module I found that worked. I’m sure there are better, more intuitive choices. I really need to update my KNOB 5 to have integer and semitone quantizer options. That was my original plan, but I got lazy in that release.

All of the Solar 42 drone voices are designed to be tuned by ear. There are no drone V/Oct inputs - all FM is linear. Voices 4 and 5 are V/Oct, but my emulator does not provide any quantizer (but it is easy to add via the patch bay). All quantization in the Solar 42 is provided by the capacitive key pad, and I did not try to emulate any portion of that. Besides quantizer, the keypad provides arpeggiator and 16 step sequencer, and more.

Definitely read the Solar 42 manual (link in first post) for the approximate range of each oscillator. I did my best to tune the range of each audio oscillator to match the Solar 42 hardware. But there wasn’t any documentation for the range of the LFOs or the voice 3,8 modulators. I just used what I thought sounded good.


When I built Omri’s version, I decided that I can’t really be arsed to hand-tune 20 voices :wink:


Yeah, that is why the Solar 42 is probably a niche product. The workflow is intentionally very old school. I opted to preserve that ethos in my emulator. It might be a good cheap test to see if you might be interested in the Solar 42 hardware.

I totally see the appeal (see also: Lyra-8) but as I was clicking this together I thought, let’s make that optional :slight_smile:

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Not aure i could even open rhis patch :joy:

On my M1 Mini (16GB) with 30fps setting and 1 thread it is:


Nice work on this. Strangely enough, I just finished a tutorial on making ambient drone. Totally different approach though!


Nice. I’m curious where the human vocal-like sounds are coming from.

Uh, that’s my attempt at a voice-over.

Wait, you meant in the patch? I think it’s probably the Surge Wavetable VCO, but Supermassive can make pads sound like a choir with the right settings.

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Hah! No, but funny response :wink: Or perhaps I asked a funny question.

I was thinking that it was the Supermassive but I wasn’t sure. Thanks.


Version 1 of the emulator had a serious bug – the FM CV for drone voices 1, 2, 6, 7 was completely broken. It didn’t effect the demo patch because it didn’t use the FM CV.

Below is a fixed version 1.1 that also uses polyphony to reduce the number of Bernoulli Switches from 6 down to 1, without changing the character of the demo patch.

Solar 42 v1.1.vcv (56.6 KB)

I also noticed that I have not quite implemented voices 1, 2, 6, 7 correctly, as I am using linear FM, but the Solar 42 is neither linear nor exponential. I hope to release a version 2 soon that corrects those voices, and also adds external inputs, and some other inputs/outputs to the patch bay.

V1 was nice though.

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Sure, as long as you didn’t attempt to use the patch bay CV input for voices 1, 2, 6, or 7 - it was totally non-functional. Version 1.1 fixes that bug.


The ELTA Solar synths do sound epic. I did the 50 a few years back.