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Stealing Thor’s Thunder – Part 1: Oscillators

By Francis Preve
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When it comes to raw synthesis power, it’s almost an understatement to say that Propellerheads’ Reason and Ableton Live have become the dominant tools for many – some might say “most” – producers.

With the introduction of Reason 4 last fall, a new synth was added to Reason’s arsenal.

Cheekily named Thor, this new synth is quite possibly one of the most powerful options available for complex sound design.

It’s complex enough that it even warrants its own tutorials.

So let’s begin hammering out the specifics of Thor.

The Oscillators

While the overall architecture is fairly straightforward – three oscillators, two filters and a modulation matrix that includes several LFOs, envelopes and a step-sequencers – Thor’s complexity resides in its modeling of several famous vintage synths for various modules.

The essentials of subtractive synthesis are covered elsewhere in our guide to synthesis, so we’ll tackle the features that set Thor apart from the pack, starting with its oscillators.

All oscillators include tuning controls and keyboard tracking at the top of their interfaces, so the essential pitch functions are consistent from module to module.

However, each of the six oscillator options is based on a classic synth, so let’s dissect each one individually.

Analog Osc

The “analog” oscillator will be the most familiar to many users, as it’s based on the most common four waveforms: sawtooth, square/pulse, triangle, and sine.

The specifics of each waveform can be found in this tutorial.

Unlike Reason’s Subtractor synth, this oscillator also includes full control over pulse width, allowing for a wider range of textures than Subtractor offers.

Varying the pulse can create everything from thin, reedy sounds to full-on electro beeps.

Even better, the pulse width can be swept via a number of modulation sources – such as an envelope or LFO – for added animation.

Multi Osc

The multi osc is loosely based on a Roland technology that was introduced in their JP-8000 synth back in 1997.

The name “multi osc” is derived from the fact that this module can recreate the sound of a stack of oscillators playing in unison, but slightly detuned for massive thickness.

Thor provides added flexibility to this feature by including eight different modes: Random 1, Random 2, Interval, Linear, Fifth Up, Oct Up/Down, Fifth and Octave.

From there, an “amount” knob determines the depth of the detuning, with maximum amounts sounding dissonant in an often-interesting way.

Small amounts yield that immediately recognizable trance lead sound that dominated that genre from 1999 until… Well it’s still going on, actually.

Modulating the amount knob with an LFO or envelope is a great way to create that THX “audience is listening” effect, which is perfect for breakdowns and buildups in a track.

Oops. Now someone is going to do that.

Wavetable Osc

Things start to get interesting with the wavetable mode, which was introduced back in 1981 courtesy the PPG Wave 2 synthesizer, which cost approximately $8000 (US) at the time of its release.

The PPG was a staple of the 80s synth pop scene, being used by everyone from Depeche Mode to Jean Michel Jarre.

This oscillator includes thirty-two wavetable options, including eleven types taken directly from the original PPG.

The position knob selects which section of the wavetable is used for generating the harmonics – the character of the sound – and can also be modulated in a similar manner to the analog oscillator’s pulse width, but with much more dramatic results.

The wavetable oscillator defaults to having the x-fade knob set to the “on” position.

This smooths the transitions within each wavetable type.

When in the off position, there is a stepped, “zippered” sound that is much more like the original, due to its vintage technology.

Whether you leave x-fade on or off is purely a matter of taste.

FM Pair Osc

Two years after the PPG was introduced, Yamaha launched their DX series of Frequency Modulation (a.k.a. FM) synths which brought complex digital synthesis technology within the range of mere mortals due its $2000 (US) price tag.

Unless you were alive at the time, it’s almost impossible to explain the importance of the DX line of synths.

The Yamaha DX7 was used on thousands of 80s pop songs, television commercial, and film soundtrack from 1983 to 1988 – and that’s really not much of an exaggeration.

FM synthesis is so important to the synthesizer world that we’ll be covering it in depth in an upcoming tutorial series later this year.

If you can’t wait until then, here’s the deeply technical description, courtesy Wikipedia.

Back to Thor…

The FM pair oscillator relies on two operators – a modulator and a carrier – to recreate a component of the overall DX sound.

In Thor’s FM Pair Osc, the carrier determines the base tuning of the oscillator (in conjunction with the aforementioned tuning knobs at the top of the module) while the modulator determines the overall harmonic spectrum of the oscillator.

Varying the value for the modulator creates a wide array of possible textures and waveforms when the FM knob is set to a value other than zero.

When the FM knob is set to zero, all you’ll hear is a basic sine wave: The foundation for classic FM operators.

So the secret to getting results from this module is to experiment with different modulator:carrier ratios, making sure to have the FM knob set to some positive value.

If you really want to nail that DX sound, it’s crucial to apply envelope modulation to the FM amount, since that’s how the DX7 was implemented.

Phase Mod Osc

With the DX7 having sold tens of thousands of units by the mid-eighties, manufacturers were scrambling to discover the “next big thing” in digital synthesis.

In 1985, Casio, a company known for their cheesy home-organ type keyboards, wowed the synth community with the introduction of the CZ101.

Based on Casio’s proprietary phase distortion method of synthesis, the CZ101 allowed users to create unique new textures by modulating the phase of a simple sine wave to create a more complex wave like a saw, square, etc.

The phase mod osc works in similar fashion, with the default sound being a sine wave that can be morphed into a blend of one or two waveforms, which are determined by the settings of the “first” and “second” parameters.

To coax unique sounds out of this oscillator, start with the default setting of the sawtooth option and slowly adjust the PM knob.

You’ll hear the sine wave gradually morph into a saw.

Now change the setting for the “second” slot to anything other than “off” and experiment further.

Because of the huge range of possible configurations, this oscillator mode offers a lot of unique possibilities – along with the ability to recreate the vintage CZ sound.

As with the other oscillators, modulating the knob with LFOs and/or envelopes is the key to creating textures with lots of dynamic character.

Noise Osc

Last but certainly but not least, the noise oscillator offers quite a few options for adding dirt to your sounds, as well as serving as the source for numerous analog percussion effects.

With the exception of classic white noise, each of the modes on this oscillator generates a type of noise that can be modified via the knob to the right of the selector LEDs.

Color mode allows you to manipulate the overall frequency spectrum of the noise source from pink (added low frequencies) to blue (added high frequencies).

In static mode, the knob adjusts the density of the noise, from just a few random clicks to grainy TV static to full-on white noise.

S/H (sample & hold) mode can morph from a stream of clicks to vintage video game effects (a la Missile Command) to standard noise.

My favorite mode – by far – is “band” mode, which adds a tuned resonant filter to the output, allowing you to create wind effects, the Duracell sound, or even the lead sound from Chris Lake’s “To The Point”.

Well, that covers the oscillator options.

In the next installment, we’ll discuss Thor’s various filter modes.

Until then…