Anyone who says they understand Absynth's "Waveshaper" is lying

The waveshaper module is poorly explained in the Absynth manual, and I think part of the reason it is confusing is the use of a sine wave as the default transfer function.

Yes, that's right - transfer function. Because the "waveform" in the waveshaper module is not actually a waveform at all. Instead, it's a graph that describes the level-dependent gain applied to each sample in the input signal.

You've probably seen transfer functions before, when you read the manual of that fancy compressor plugin you downloaded. Well, the waveform in Absynth's waveshaper function is similar, except that the input signal zero voltage is centred mid-way along the x-axis.

The first stage in understanding how to use the waveshaper is to create a new transfer function in Absynth's Wave window:

Identity function

Looks like a reversed sawtooth doesn't it? Well, just remember that it isn't a sawtooth. In fact it describes an identity transfer function, where the output (y-axis) is always equal to the input (x-axis). This means that with the identity function loaded, the waveshaper makes no effect on the sound. Try it.

Does it make sense now? Good. With this knowledge, we can begin to model saturation characteristics that are observed in analogue audio circuits.

When analogue circuits are driven hard they can become non-linear. You can model this by modifying the identity function in the Absynth wave editor. Remember to modify the waveform at both ends, as the transform function maps the input signal level from negative to positive voltage values. Here I have simulated a "diode-clipping"-style saturation effect in the Absynth Wave window.

Transfer function to simulate hard clipping

You can see the result of the waveshaper transform on a sine wave input on the image below.

Hard-clipped sine wave

It's easy when using the waveshaper to overcook your signal and end up with grating noise. A useful technique for applying waveshaping in a more controlled way is to use Absynth's morph waves functionality.

Create a new morph wave and in one slot place your own transfer function, and in the other slot the identity transfer function. By morphing between the two you can adjust the amount of distortion you add to your signal, and hopefully end up with some more musical results.

Using morph waves to control waveshaper intensity

In the clip below I created an 808 style bass part and experimented with various kinds of waveshaping distortion. Enjoy!

Waveeshapey by pedalsteeldrummer

Related links

• Absynth: http://www.native-instruments.com

SoundMagic Spectral plugin suite

I discovered Michael Norris' "SoundMagic Spectral" plugin suite a few years ago. This set of plugins offers digital spectral processing techniques which are rare to find elsewhere, and the fact that they are (currently) free is pretty amazing.

Spectral processing involves the manipulation of a sound by analysing its contents at a particular point in time (or "window"), and then chopping it up into many small frequency bands, or "bins". These bins can then be re-arranged in various ways to produce all sorts of strange inharmonicities and filtering effects. In addition, by sampling a sound at large intervals, and then reconstructing it by interpolating between each window, a number of characteristic blurring or drone type effects are possible.

One of my favourite plugins in the suite is called the "Spectral Tracing" plugin. This allows you to filter a sound based on the loudness of each frequency component in the spectrum.

Here I have processed a drum loop, but retained only the loudest frequency components of the sound. The result is a really atmospheric blunted, throbbing texture.

Blunted by pedalsteeldrummer

Here I have taken some factory noise and retained only the middle amplitude frequency components. Result: an eerie underwater effect.

Underwater by pedalsteeldrummer

With these plugins, a good deal of experimentation with different kinds of source material is required, and for Spectral Tracing I find that very dynamic sounds work best.

I also find that it is important to use a large number of frequency bins, otherwise a lot of brittle metallic artefacts are produced in the effected sound. In small amounts though, this metallic quality can be quite atmospheric, so it is worth experimenting with the "FFT size" parameter.

You can find the SoundMagic Spectral plugins (Mac OS X only) here.

Related links

• SoundMagic Spectral for Mac OS X http://www.michaelnorris.info/soundmagicspectral/index.html

Horror drone sounds in Absynth

Drone sounds are indelibly associated with the genre of horror movie that emerged in the 1970s. Classic scores such as Suspiria (1977) by Goblin, and John Carpenter's The Fog (1980) make use of eerie wordless choirs and brooding analogue synth basses.

As well as these classic synth elements, contemporary horror scores make use of drone sounds that could be described as "organic", bringing with them associations of metal, glass or liquid.

I want to demonstrate a simple technique for turning any percussive audio sample into an organic drone sound.

Percussion sounds make great source material for these sorts of drones, because they tend to contain a rich mix of noisy partials. Also, the way in which these partials decay can be used to give a drone a very organic shifting timbre.

I'm going to use the granular sample module feature of Absynth to manipulate my source material. I think that granular sampling is overlooked for one of the simpler tasks it can achieve - it is extremely useful for slowing down audio without introducing pitch-shift artefacts.

Here I have taken a sample of an orchestral bass drum and by modulating the sample start envelope with a gentle slope I can make the sample play at a slow speed. Continuously looping the sound produces a pleasingly organic sound, but the attack envelope of the sample still makes it recognisable as a bass drum.

BassDrumLoopOrig by pedalsteeldrummer

By manipulating the oscillator amp envelope, I can remove the percussive click of the attack portion of the sound.

Then, by increasing the channel gain as I move the sample start point through the source file, I can turn the percussive decay portion of the sound into a continous sustain.

Send the sound through a suitably cavernous reverb effect, and the result is a beautifully mysterious, rumbling drone sound. I particularly like how the subtle fall in pitch of the bass drum as it decays is transformed into an eerie moaning sound.

BassDrumDrone by pedalsteeldrummer

The beauty of this patch is that I can produce a whole variety of organic drone sounds by simply replacing the source sample with other percussion material. Below is a selection of alternative drone-like sounds. Enjoy!

AbsynthOrganicDrones by pedalsteeldrummer

Related links

• Absynth: http://www.native-instruments.com

Evolving pads in Logic Sculpture

Sculpture is the physical modelling synth that is shipped with Logic Pro. It was released with Logic Pro 7 way back in 2004 but I have to admit that I've not given it a lot of attention until recently.

The problem I find with synths that claim to be able to accurately model real-life acoustic sounds is that if you want those type of sounds it is much easier to use a sample library.

What's more, physical modelling is a very different approach to synthesis than subtractive or FM, and I find that a lot of trial and error is required to get a feel for how the different parameters affect the resulting sound.

Just recently Native Instruments released a new Reaktor ensemble called Prism which claims to be able to produce "organic soundscapes, percussive keys, flutes and bells". Although Prism is not strictly-speaking a physical modelling synth, it inspired me to revisit Sculpture and make the effort to get a better understanding of how it works.

I have discovered that by using the "morph pad" that Sculpture incorporates you can come up some very beautiful evolving pad-type sounds.

The concept behind the morph pad is actually very cool (same as the "remix pad" concept that has been adopted by Camel Audio's Alchemy synth). Once you have programmed your basic pad sound you use the morph pad (pictured) to store "snapshots" of up to 5 variations of your patch. You create variations of your patch either by manually moving the synth parameters to new positions, or by using a "randomise" function that is provided. To create a sense of movement in your pad sound you draw an envelope on the morph pad which slowly modulates the synth parameters - and therefore the resulting sound - between each patch variation.

The reason the morph pad works so well is because changing the parameters of your physical model even slightly can produce very unexpected results. To create a similar kind of movement in a subtractive synth would require modulating many parameters with many different LFOs and/or envelopes.

Sculpture's physical modelling architecture uses the concept of "objects" rather than oscillators as sound sources.

I find that the most useful object for creating pad sounds is the "blow" model, being able to produce a range of smooth metallic or glassy sounds, rather like a waterphone or bowed vibraphone.

The "bow" and "wide bow" objects seem to produce very noisy, scratchy sounds which sound to me fairly harsh and unpleasant, kind of like a beginner violinist!

Evolving pads in Logic Sculpture by pedalsteeldrummer

Related links

• Logic Sculpture: http://www.apple.com/logicstudio/logicpro/
• Reaktor Prism: http://www.native-instruments.com

I went down to the crossroads...

I bought Absynth back in 2001 when it was released as a standalone application on the Mac. It was one of the first software synths,  and in a world of analogue synth emulations it remains one of the most unique.

As a distinctly non-commercial synthesiser, I think Native Instruments have managed to do a good job of finding a marketing niche to fit Absynth in. A "limitless spectrum of unusual, evolving sounds" as they describe it.

Unfortunately, as seems to be synth marketing law these days, they also encourage potential customers to view Absynth as a synth that can do everything.

Consequently the factory preset  library is filled with an enormous number of - in my view - unremarkable "bread-and-butter" synth sounds.

Personally, I like a synth to have some character, and that means there are certain types of sounds it will do well, and certain types it won't. Absynth is definitely a synth with character and I wanted to try to articulate the sound-world that I think Absynth lives in.

As well as being a fan of synth sounds (of course) I am huge fan of blues guitar music, and occasionally I dig out my Squier Strat to exorcise some middle-class angst.

What I love about blues guitar is the habit that blues guitarists have to dirty up their sounds.

Whether it be the use of bottleneck slide, the rattle of finger picks on a resonator guitar, the subtle use of string bends, or the sound of a fuzzed-up, overdriven guitar amplifier, this affection for distorted sounds is clear.

I believe that this tendency actually originates in one of the sources of the blues, traditional African folk music.

The thumb piano (pictured to the right) often has objects affixed to the soundboard to give it a rattling sound. Thin membranes are are added to the gourd resonators of African marimbas to add a nasal buzzing. And the steel drumming tradition that emerged in the caribbean actually used instruments built from oil drums discarded by the US Navy!

And I think that Absynth very much belongs in this sound world. All the sounds I end up programming seem to have this impure, distorted quality.

If you want big fat supersaws, lush chorused pads or crystal-clear FM sounds, I think you need to look elsewhere. But if you want to conjure up dry, warped basses, scorched, resonating soundscapes or scraped, twisted percussion sounds, then dive in!

I Went Down to the Crossroads... by pedalsteeldrummer

Related links

• Absynth: http://www.native-instruments.com

Attributions

• Photo of slide guitar by Lubos Bena, available under a Creative Commons Attribution-Share Alike 3.0 Unported license
• Photo of Mbira Dzavadzimu (thumb piano) by Alex Weeks, available under a Creative Commons Attribution-Share Alike 3.0 Unported license

Voice: init

First post!

I wanted to start this blog to share my passion for all things synth and sound design. Hope you find something of interest here!

Giles (pedalsteeldrummer), October 2010