Programming iPad Synths for Breath Control, Part 1

Arturia’s iSem synth has been available on iOS for over three years, but I’ve never been compelled to pick it up until now. Why now? Well, I had $10 burning a hole in my pocket, I have recently started using the Cubasis DAW, it comes with 500+ presets to explore, it is still one of the very few synths to support the Audio Units protocol for integrating into DAWs, and finally, the mod matrix looked like it could support programming for breath controller. That’s a lot of mileage for $10! In this article, we’ll scratch the surface on adding breath control to iSem patches. With this knowledge you’ll be ready to “breathalyze” your favorite patches and use them for live performance. In part 2, we’ll look at using this knowledge in the “studio” to integrate into iPad DAWs like Cubasis.

Before we start, let’s think about what it means to program a synth for “dynamic expression”. This would be the same process if you were using a mod wheel, keyboard aftertouch, or in our case, breath control. In any case, you need a controller that generates a dynamic signal and “does something” “inside” a note. So whatever this controller is controlling, it does it without hitting a new keyboard key. Ideally, you want the breath input to do more than one thing at the same time. If you think about an acoustic instrument, when you blow harder into a saxophone, the sound gets louder, but it also gets brighter, noisier, raspier even. All at the same time. We’d like to mimic those things in our synthesis.

So let’s start with a simple patch with no breath control:
As you can hear, nothing happens to each note once it starts. This is almost the stock iSem patch “Simple Clarinet”. I’ve added a little bit of portamento, chorus, and delay but I don’t think I touched the other knobs – not much anyway.

Here is the same patch with breath control added:

Sounds a lot different, doesn’t it? Let’s pick apart why that is. Here’s the mod matrix:

First, notice that Breath or CC2 is not listed as a modulation source in iSem. (There are synths that do including Addictive and Thor, but we’ll save those for another time.) The only performance controllers are Mod Wheel and Aftertouch. We will choose Aftertouch. This is either a minor annoyance or a small hurdle depending on your hardware. Some wind controllers, like the Akai EWI 4000s and 5000, can be configured to output Aftertouch (AF) messages directly instead of Breath (or even in addition to, though that would only increase the amount of MIDI data generated and is just wasted processing). Other controllers like the WX5 do not have this capability. To use them, you will need a “MIDI mapper” to translate CC2 to AF before it is passed to the synth. The easiest to use is probably the free FreEWI app but there are others such as MIDIBridge as well as hardware solutions. (Details can be provided in a separate article if there is interest.)

There are 8 different modulation slots and 26 possible modulation destinations for each. This patch is relatively simple, only using 4 of the slots. The first three will probably be used in just about every breath controlled patch regardless of the synth:

1. VCF Frequency – since the Amount knob is positive, this increases the filter frequency the harder you blow, making the sound brighter.

2. VCF Resonance – increases the resonance of the filter, accentuating the high frequency content even further.

3. VCA AM – amplitude of the “voltage controlled amplifier”, I.e. volume, so the sound gets louder the harder you blow. (Curiously, the VCA is not shown in Main synth page but the amplitude and pan can be modulated anyway.)

If a synth can’t control filter frequency and volume via breath at the same time, I would go so far as to say that synth is useless for breath control. I gave up on using Sunrizr for this purpose as I couldn’t figure out a way to control both at once.

4. Envelope 1 Attack – This one I hesitate to mention as I’m actually not sure it’s working in this patch, but I want to point out that the Amount is negative. The intent here is to decrease the attack time with higher breath pressure thus giving a slower/smoother/legato attack with low pressure and a quicker/harder/staccato attack with higher pressure. But the bigger point here is there are a lot of parameters to explore and just see what they do.

Just one more consideration for now: why choose Aftertouch instead of Mod Wheel? Two main reasons. First, the EWI breath sensor cannot output Mod Wheel but the glide sensor can. So that gives another dimension for expression (not used in this patch). But second, the on-screen keyboard iSem generates Aftertouch when you hit a key and then move your finger vertically. This means you can design patches right on the iPad without plugging in your wind controller. Very handy.

So go to it. There are 500+ presets and 26 modulation destinations to explore. That should keep you occupied for a while. I’d love to hear what you come up with.

So far, you know enough to launch iSem in standalone mode, plug in your wind controller, and play. Run the headphone jack out to a keyboard amp or PA, and you’re ready to rock the house.

What about integrating this into other iOS tools like effects apps and DAWs? We’ll explore that in part 2.


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