K1v: Making Sense of AM

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During our Editing Parameters tour, we found the K1v AM S1>S2, and AM S2>S1 parameters in the Source Common section. Let’s check out AM and its uses for sound design within the K1v (and Kawai K1). There aren’t many traditional synthesis techniques available on K1v, mainly because of the limited modulation sources and lack of filtering. Ultimately though, “synthesis” is creating new sounds and waveforms. K1v has a few methods to do this, and AM (Amplitude Modulation) is one way to generate new waveforms beyond the 256 included.

What is AM?

The term AM is slightly confusing, as many would argue that using an Amplitude Envelope to modulate the waveform output of a synthesizer is Amplitude Modulation. The AM we’re talking about in K1v is the synthesis that occurs when you use the amplitude of the output of one waveform to modulate the amplitude of the output of a second waveform at audio rates. Having designed synthesizers in the past, I referred to a couple of textbooks I have around for clarity. In the K1v case, we’re either taking S2 and multiplying it by the output of S1 (S1>S2), or vice versa. S2 can be called the Carrier and S1 the Modulator in this example. The outputs of both S1 and the modulated S2 are then available for use in the final output.

There are also times when you will encounter the terms “Ring Modulation” and “Balanced Modulation.” These are examples of AM, but slightly different, in that the output is the sum and the difference of the two input waveforms. Tthe original Carrier or Modulator waveforms available for output. In essence, you get the resulting “side band” and noisy part of the synthesis operation. You aren’t adding sidebands or noise to the original waveform as in AM. K1v AM is that we’ll use it to create new waveforms, both static and dynamic, beyond the factory 256

For more detail about AM synthesis, I’ve listed two highly technical books in “Resources” that cover this topic (and more). I also recommed this article by Philip Mantione over at The Pro Audio Files. It is excellent and has better diagrams than I can make (LOL). In this post, we’re focusing on how it works in K1v.

Editing the AM parameters within the Common Section
How AM Works in K1v

In K1v, we have two signal paths to apply AM. If this is a two- or four-source patch, we can apply AM in the S1/S2 or the S3/S4 combination. As mentioned before, we can also select which oscillator is the carrier and which is the modulator. You are selecting the primary “Carrier” waveform that continues through the signal path and has the AM sidebands added.

Let’s start with the SE Init Patch I’ve included in the Resources below. The patch is a two-source sound with no modulation, both waveforms set to Sin 1st, and volume programmed at a level that won’t generate digital distortion in the signal path. Also, S2>S1 AM is enabled. At first play of this patch, we’ll see a regular, sine-wave output on the oscilloscope. No AM is occurring because there is no output from S2, due to the volume of Source 2 being zero.

Now, let’s increase the volume of Source 2 to 100. We’ll now note the effect of the Amplitude Modulation of S2>S1, which adds a harmonic, even though the waveform frequencies are the same. Just adjusting the volume of Source 2 in this patch allows the generation of 100 new waveforms (one for each volume step of Source). Granted, these are reasonably boring organ-like waveforms, I’ll give you that. Run some experiments with S1 programmed to different course tunings. The most musically interesting results will be in harmonic intervals that are common in chords, like fifths and octaves. 

Using Source 2 > Source 1 Amplitude Modulation (AM)
Let’s make it more interesting

We’ve seen basic AM in operation. Let’s make it more dynamic and sonically interesting than organ sounds, please. There are some ways to make the K1v’s implementation of AM more interesting – let’s take a look at envelopes first. Start at our SE Init Patch. Adjust the AMP Envelope of Source 2 to be a decaying envelope, with Sustain (S) value at zero and the Decay (D) at 40. If we now repeat our experiments above by changing the pitch, we get something more dynamic that resembles a percussion setting on an organ. Program S2 Coarse to +9 before we move onto the next step.

Next, add velocity modulation to S2 by increasing Vel > Level to +25. Now, we have a patch whose waveform output dynamically changes with incoming velocity. At this point, we can also increase the Output level of S1 to 90 to avoid distortion in the signal path. Our last change for this waveform combination will be to set S2 Coarse to +24 before moving on.

Let’s make it really interesting

Our final experiments in this post will be to add even more harmonically interesting inputs to the K1v AM calculations by changing input waveforms. Dynamic AM is interesting with just sine waves – we can create PWM simulations using this approach. Taking harmonically complex waveforms like Pianos and modulating other waveforms at audio rates becomes FM-like in its result.

For S2, select waveform 150, Piano 1. What we hear now is an “FM Tine” class of output, complete with dynamic response to velocity. Now we are getting somewhere. 

There are thousands of combinations of waveforms that can extend the sonic palette of K1V using AM in just the 2-source patch mode. I recommend running lots of experiments with square Carrier waveforms, and moving on to modulating harmonically complex waveforms like strings and pianos with other harmonically complex waves.  For example, we’ve only just touched the surface with Source 2’s envelope having a rapid decay. What if it had a slower attack?


As a final insight into what can be done with a synthesizer with limited resources, such as K1v, I’ve included this short sound sample below of a Saw wave carrier, being modulated by the Piano 1 wave with a slow attack, running through the Blackhole Eventide plug-in. Additionally, just because you don’t think you need to invest in Eventide plug-ins, there’s another progression with the factory Reverb and Chorus built into Studio One. To me, this is a great example of what K1v can do with a bit of help – it certainly isn’t boring, at least to my ears. I can play with these sonically interesting pad sounds for hours (I did for this demo).

Wrapping up

We have looked at how AM works in K1v and some applications for its use in sounds. We’ve said all along in this series that there isn’t a large number of tools for synthesis in K1v, but that doesn’t mean you can’t get great sounds out of it. Also, it doesn’t mean you can’t synthesize new sounds using even the limited tools – it depends on your outlook and what you are willing to try. With even basic tools, we created, in my opinion, an excellent pad using built-in effects.

Exploring the AM synthesis capabilities of the K1v opens up a whole new dimension of sound design possibilities. By delving into these features, we’ve uncovered yet another layer of this versatile synthesizer’s potential for creating rich, complex timbres. At SoundEngine.com, we aim to empower musicians and producers with the knowledge and tools to push their creative boundaries. The K1v’s AM synthesis is a perfect example of how understanding the intricacies of an instrument can lead to innovative and expressive sound creation. We encourage you to experiment with these techniques in your own productions and to continue following our K1v series. There’s still so much to discover about this powerful synth, and we’re excited to guide you through every aspect of its capabilities. Stay tuned for our next installment, where we’ll uncover even more ways to harness the K1v’s sonic potential and elevate your music to new heights.

Resources

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