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Moppeltron v1.1 VST
Moppeltron employs the Discrete-Summation Formulae (DSF) synthesis technique proposed by James A. Moorer. This technique has capabilities similar to those of frequency modulation, yet it has the advantage that the number of partials can be exactly specified and that also one-sided spectra can be generated. By morphing between two mixes of DSF parameter sets, Moppeltron is capable of synthesizing a wide variety of sounds and effects.
I created Moppeltron using Synthedit, yet it doesn't use native Synthedit oscillators but a unique DSF oscillator which I coded in C++. For v1.1, I also coded a new ADSR module which works just as the native SE module but operates faster.
How it's used
OverviewThe starting point of synthesis is the harmonics unit, where two DSF parameter sets are defined, each of which describing a waveform. The two sets are then combined by the morphing unit using one of five different control modes to synthesize the final waveform. In particular, the parameter sets can be mixed utilizing one of the two mix sliders to synthesize a static waveform, or the synth dynamically warps between the two mixer settings using one of the two Attack-Decay-Sustain-Release (ADSR) envelopes or the low frequency oscillator (LFO). Finally, the volume of the resulting signal is adjusted by an ADSR envelope and a gain slider.
HarmonicsEach of the two DSF parameter sets describes a waveform as the sum of sine waves at particular frequencies (commonly called harmonics or partials). One partial, hence called center frequency, is special in that it is always generated. The center frequency is determined by the currently played note and tuned with the respective PITCH knob.
SIDEBANDS is the number of additional partials on either side of the center frequency. If SYMMETRY is set to 1-SIDED, then all additional partials will be greater than the center frequency, ie. in the spectrum they will be on the right side of it, making it the fundamental frequency. If SYMMETRY is set to 2-SIDED, then the partials on the right side will be mirrored to the left side, making the frequency spectrum symmetric at the center frequency.
For each of the two parameter sets, the frequencies and amplitudes of the resulting partials can be defined as follows. The frequency of the i-th partial is
freqc + i * ( freqc * m/c + offset)
where freqc is the center frequency, m and c are the left and right values of the knobs denoted as M:C-RATIO, and offset is the value of the knob M-OFFSET. That is, the distance between two subsequent partials is constant, and it's described as a multiple of the center frequency plus some offset.
The amplitude of the i-th partial is
a ^ i
where a is the value of AMPLRATIO. That is, for amplitude ratio values smaller than 1 (greater than 1), the partial amplitudes decrease (increase) as the distance between the partials and the center frequency increases.
Note 1: If offset=0 and two-sided symmetry is chosen, the resulting spectrum is the same as that synthesized by frequency modulation with freqc as carrier frequency and (freqc * m/c) as modulating frequency, the difference being that the FM spectrum would be infinite.
Note 2: If offset=0 and integer values are chosen for m and c, the resulting spectrum is a harmonic series.
Note 3: Partials with negative frequencies, which can occur by the definition above if m or offset is negative, or if the spectrum is two-sided, will be mirrored. For example, a partial at "-100Hz" would actually be audible at +100Hz.
MAXFREQ is the maximum allowed frequency of the partials. Only partials lower than that value will be generated. MAXFREQ is usually set to 22000, ie. about half the supposed sampling rate of 44kHz, to avoid aliasing. Still, Moppeltron operates at any sampling rate, and MAXFREQ can be set to arbitrarily large values using the text entry field.
MorphingThe two DSF parameter sets are combined by the morphing unit. There are five different morphing methods which can be chosen with the MORPHCONTROL selector:
If you want to reset the MIDI-CC -> Parameter mapping to its default, keep the LEARN button pressed for 5 seconds. But be cautious: This will not alter only the mapping of the current Moppeltron instance but also that of any Moppeltron instance sharing the same MAP-ID.
This is because the mappings are stored centrally, and Moppeltron instances that share the same MAP-ID also share the same MIDI-CC mapping. So if you want use more than one MIDI-CC mapping, you have to alter the MAP-IDs accordingly. For instance, if you have several projects, and you want each project to have a unique MIDI-CC mapping of its own, assign a certain MAP-ID, eg. '0', to all instances in the first project, then another MAP-ID, eg. '1', to all instances in the second project, and so forth. And if you want to use different mappings for different instances within one project, you have to assign different MAP-IDs to them as well. By the MAP-ID control on the Moppeltron panel, you can assign 100 different IDs (0-99).
One extra hint: The mappings are stored as plain text files in the Moppeltron plugin folder, in folders named mpt1100, mpt1101, and so forth. So you can, for instance, make backups or copy and paste your own default mappings.
MiscGAIN limits the overall volume, and the ADSR1 envelope controls the dynamic volume change once a key is pressed.
If the MONO button is lit, then only one voice is played (instead of 8, the default).
SLIDE is the speed at which notes slide. To make notes slide, a key must not be released before the next key is pressed. Otherwise, if keys are always fully released before the next key is pressed, no sliding will occur. You'll figure out how it works if you use the 'Cat' preset and slide with the mouse on the piano keyboard while keeping the left mouse button pressed. If the 'T' field on the piano keyboard is lit, pressed keys will remain pressed until the 'T' field is unlit again.
BENDE RANGE is the pitch bend range measured in half tones. If you're using a pitch bend wheel, you may have to alter this parameter to get the desired effect.
InstallationPut the file Moppeltron.dll into your VST Plugins folder.
Thanks toJames A. Moorer (author of "The Synthesis of Complex Audio Spectra by Means of Discrete Summation Formulas", http://www.jamminpower.com/main/articles.jsp)
Darren Hester (photographer of the original texture that has been used in the panel background, http://www.pixelperfectdigital.com)
Jeff McClintock (creator of Synthedit, http://www.synthedit.com)
David Haupt (creator of the MIDI ControlMeister module,http://www.dehaupt.com/SynthEdit/index.html)
firstname.lastname@example.org (Burkhard Reike).
VST is a trademark of Steinberg Soft- und Hardware GmbH, Germany.
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