Thor Polysonic Synthesizer Part 3: Modulation Sources

Last week we talked about the sound generation and subtractive filtering components within the Thor Polysonic Synthesizer.  With knowledge of these components you can create a wealth of unique sounds.  But no matter how hard you try, these sounds won't seem as "alive" or unique without the use of some sort of modulation.

Thor offers two types of modulation: LFO's and Envelopes.  

LFO's

LFO's - or Low Frequency Oscillators - are similar to oscillators that you would use to create musical pitches however, LFO's operate at a slower frequency (0.07 - 99.6 Hz in Thor at 20 BPM).  These are the oscillator waveforms available in Thor's LFO 1 and LFO 2:

These include Sin, Sawtooth, Square, Triangle, both rigid and smooth Sample and Hold (i.e. Random), and exponential waveforms as well as both stepped and stepped-ramp waveforms (with multiple step-counts per cycle).  Using the modulation bus matrix (which I will discuss later), you can modulate almost any parameter within Thor with any of these waveforms at a set rate and to an adjustable amount.

Thor offers two LFO sources (aptly named, LFO 1 and LFO 2) for modulation.  Both LFO's offer independent waveform selection, tempo sync, key sync (restarting the LFO's position when a note is played) as well as rate and delay rotaries that run independent from one another.  LFO 1 has the additional parameter called "keyboard follow" which determines how the position of the notes played effects the rate parameter.  As the follow parameter is increased, the rate becomes more and more influenced by the position of these notes (i.e. higher notes = higher rate frequency).

Envelopes 

Wikipedia Commons

Envelopes are modulation sources that divide a sound or a selected parameter into sections:

A.D.S.R.

Attack - time to ascend from 0 to peak level

Decay - time of descent from peak level to sustain level 

Sustain - time of sustained level

Release - time of descent from sustained level back down to 0

By adjusting the time lengths of each of these stages, you can either subtly or drastically change the behavior and character of the effected sound source or parameter.  Thor offers four individual envelope generators: 

Amp Envelope

The Amp envelope effects the amplitude of your sound oscillators.  Each slider can be used to  determined the time duration of each stage - except the Sustain slider.  The sustain slider determines the level at which the amplitude is sustained.  It does not affect time because the sustain duration ends when a note is released.

Filter Envelope

The filter envelope functions in the same manner as the amplitude envelope, except this envelope modulates the behavior of Thor's filter frequencies.  As you may recall from my previous post on Thor's filter section, the individual filters have rotaries that can control the amount of influence the filter envelope has on their frequencies or parameters.

Modulation Envelope

The modulation envelope is slightly different in comparison to the amplitude and filter envelopes which both have a predetermined target.  It does not automatically modulate any parameter without prior assignment in the modulation bus matrix.  The mod envelope offers a tempo synchronization function that changes the fader parameter from milliseconds to steps ranging from 1/32 note -  to four full bars in length.  As you may notice from the image above, the modulation envelope does not have a sustain function.  Rather, its sustain is level is preset.  There are two additional features that are introduced with the modulation and global envelopes: Delay and Loop.  The Delay function does exactly what it says; it allows you to delay the onset of the modulation by a set time or beat length.  The loop function loops the delay, attack and decay stages repeatedly until a note is released (if "Gate Trig" is engaged).

The global envelope is similar to the modulation envelop.  It does not have a predetermined modulation target, so it only modulates parameters set in the modulation bus matrix.  The Global envelop offers both the delay stage, tempo synchronization and loop functions that the modulation envelope has.  However, the global envelope includes a sustain level fader and also incorporates a "hold" stage that determines the length of time the peak level is sustained before the decay stage begins.

I hope you guys enjoyed these articles on Thor.  Next I will be talking about the Grid of Death modulation bus matrix, the step sequencer, as well as the delay and chorus components.  Thanks for reading!