These are incredible times.... A $10,000 classic Moog synthesizer as a $30 iOS app? You'd better believe it, but even interesting is just how very good and usable this analog synthesizer emulation is.
Moog Model 15 Ribbon Controller

User Interface

Moog Model 15 in portrait mode.

Modules Included

Audio Engine

Moog Model 15 Arpeggiator


Ableton Link

Audio & MIDI Bridge

Educational Aspect


Moog have put a lot of care and attention to every aspect of the app.



Synthesis 101
The Filter
by Bob Moog Foundation

"Rishabh Rajan is an award winning music producer & educator currently based in New York. He produces electronic music under the name code:MONO & hosts a YouTube channel featuring music and live mashup videos using performance controllers like the Ableton Push. He is also a sample library developer having worked with companies like Bela..." Read More


Hi, Rishabh Rajan

You said "Now, there are some limitations to the sound. While modulating the oscillators or filter cutoff at audio rate the sound is a bit controlled and unlike what you would normally expect from an analog synth. In other words, the sound doesn’t really break apart and scream like it does on a hardware analog synth."

This is false. Here is a example of the Model 15 doing these sounds:

Here is the patch:
Your audio example proved exactly what I was saying :)
How so? The FM depth is limited just like on the original synth. I think this is what you are referring to? Here's what moog music had to say about it on the audio bus fourm:

Audiohub said:

Audiohub May 7
"I've got another question for the Moog guy, although I haven't seen him posting here lately.
Are you still monitoring this forum?

I've noticed that the most that you can increase the frequency of the two 921b oscillators by using the DC Modulate jacks is just 1 octave up or one octave down. This seems broken, as it severely limits the ability to do useful FM by modulating one 921b with the other, and also really limits the hard sync tonal range if you're modulating the synced oscillator with an envelope generator for that classic sync sound.

On a hardware 921b module, the oscillator can be modulated much farther than this, allowing it to create a much wider range of sounds.

Can this be fixed?

Also, thanks for your previous answer about normalling the inputs of the 3 reversible attenuators. Although I agree that this isn't part of the recreation of a vintage model 15, I still hope that you might consider it in a future update because of its usefulness.

I don't really see this app as a slavish recreation of the 15, because it really is a lot better in a number of ways, what with the Midi and Audio patchbay, the Voltage Controlled delay, Voltage Controlled reversible attenuators (I don't think Moog ever made these for the Modulars, although they certainly should have) and even nice touches like including the hard sync to replace the less useful strong sync that was on the original 15.

There is a neat trick you can use to extend the range of the 921b modulation...
If you use an app like MidiBridge, you can route the Model 15 Midi Out to the Model 15 Midi In.
Now, you can route the envelope generator to, say, the CC 16 Midi Out on the Midi panel. If you assign the oscillator Frequency knob to CC 16, now you can go 2 octaves up and down. Better, but still not great.
You can also assign CC 16 to the Oscillator Range switch (yes, you can assign the same CC# to multiple destinations if you want) and now you can push the frequency up via the envelope generator quite a bit!
Not very convenient, but for the determined programmer with access to an app like MidiBridge, there are at least some options available."

MoogMusicInc. replied:

"We'll look into this, but if memory serves well the DC modulate input is indeed limited between -1V and +1V in the hardware specifications of the 921B. The AC modulate input doesn't have this limitation."

Audiohub replied:

Audiohub May 7
"Nice to see that you're here! Much appreciated!

I just went and fired up the hardware Modular, and you are indeed correct!
Somehow I was sure that that input had a much wider range, but in reality, mine can only be pushed about 1 1/3 octaves before it rails out. The AC modulate on the app doesnt seem to go any further, although since it's AC coupled that makes it harder to tell if you use the envelope generator (it won't stay at pitch as the cap simulation blocks DC)."

Original post link:
I didn't know the original hardware had the same limitation.
Also, I should have defined clearly what I really meant by 'break apart'. I suppose on any level once the sound is Frequency Modulated, it does break apart. Just like in your example. But I was talking about how it happens on a system where the FM Index is not limited to such a narrow range. For example in the Eurorack world, a module like the Make Noise DPO just obliterates the sound when the exponential FM Index is up.

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