Oscillators
Zebra’s oscillators are pretty powerful beasts. As these introduce new forms of synthesis it is a good idea to read this section even if you understand how a basic oscillator works.
Oscillator module
The oscillator module contains control over the tuning, mix, effects and phase of the oscillator. The module is collapsable to save space in the rack. When collapsed the controls for mix, effects and phase are not accessible. Clicking on any of those tabs in the module will expand the module again to show those.
Oscillator presets
In Zebra2 you can create presets for the oscillators themselves to speed up the process of sound creation. Click the box “default” in the oscillator modul to bring up a file selector and choose the preset. Currently there are no oscillator presets included, but these will start to appear in future updates and will also be available from the Zebra2 download page.
Please be aware that if you have setup modulations (like WaveWarp modulated by an LFO), the modulation source and the modulation amount will be saved but the settings of the modulation source will not be saved with the oscillator preset. That’s why recalling a preset may not sound 100% the way it was, when it was saved.
To save your own oscillator setup ctrl-click or right-click the box “default” to bring up the Zebra2 save dialog.
The module presets are located in these folders:
Mac:
Local:
MacHD/Library/Application Support/u-he/Zebra2/Modules/Oscillator/
User:
~/Library/Application Support/u-he/Zebra2/Modules/Oscillator/
Windows:
C:\Program Files\u-he\Zebra2\Modules\Oscillator\
Tuning
Each oscillator can be tuned in a range of -48 to +48 semitones, in steps of 1 Cent. So, if the tune display reads “7.24″, the oscillator is tuned 7 semitones up, plus 24 Cents. Tune has a direct modulation source. Without needing to go through the Modulation Matrix, you can directly set a modulator. The tune modulation controls the oscillator’s tuning modulation in a range of -48 to +48 semitones. Vibrato assigns LFO1 to modulate tuning by +/- 1 semitone. Keyscale determines how the comb filters pitch reacts to the note played. At 100 it is standard semitone per note.
Mix
This oscillator tab controls the output of the sound.
The volume knob controls the output volume of each oscillator.
In addition to the volume there is a volume modulator ready to use, set the modulator source from the mod pop-up menu and the modulation value with the mod knob.
Choose the unison mode from the pop-up menu, the options are single, dual and quad. The width knob determines the position in the stereo panorama.
Set the pan with the pan knob. This can be modulated by choosing a modulator from the pop-up menu and setting the modulation amount on the knob.
Waveform
The waveform editor is the core of Zebra2s synthesis. This is where you can draw waveforms or additive spectral shapes. There are 4 different modes you can choose from using the Waveform parameter to the right of the drawing area.
There is a keyscale keyboard pictogram in this area that allows you to control the volume accross the keyboard. This is useful if you’ve programmed a sound that has a high peak as a result of a resonating filter around a particular pitch area. With this you can lower the volume for that area. Of course there are other applications, like split sounds where the lower registers are used for a bass sound and the upper register for leads or pads.
Below the keyscale is a velocity scale controller use this to exclude or scale certain key velocities. For example if you want one oscialltor to sound when played softly and one for loud playing. The lines and dots represent the highest velocity the OSC reacts to. In other words this works like a velocity filter: it filters out all notes played above the set velocity.
- GeoMorph:
Choose this mode to draw a waveform using up to 32 points. The first and last point are identical to insure smooth cycling.
Editing options:
Click: select a point (green)Shift + Click: adds/removes points from selection
Drag: freely moves points
Drag across several points: selects by drawing a rectangel.
Alt or command (Mac), Ctrl or Alt (PC) + drag: change the slope to the left (right respectively)
Right-click on one selected point: opens a context menu to remove a point or to change it’s slope.
Right-click with several points selected: access a context menu to apply functions to the selected points.
Right-click in empty area: add point or apply functions to the whole waveform.
Ctrl + command + click (Mac), alt + right click (PC) in empty area: add point.
- SpectroMorph:
Looks and feels like GeoMorph but is a completely different animal.
In this mode the display doesn’t show a waveform but an additive spectrum consisting of 1023 harmonics. The harmonics are logarithmically distributed accross 10 octaves. The lowest 10th of the display controls the fundamental, the next 10th the first two harmonics etc until there are 511 harmonics in the right 10th. The highest point is always set to zero.The volume is also scaled logarithmically.
A horizontal line creates a sawtooth.
All the controls are the same as before.
- GeoBlend:
Draw a waveform using 128 evenly distributed points.Option-drag (Mac), ctrl-drag (PC) draws a straight line.
Command-drag (Mac), alt-drag (PC) resets the points.
Right-click: opens a context menu with options to blur, sharpen or maximize the wavefrom.
- SpectroBlend:
Identical to SpectroMorph except the waveform spectrum consists of 128 harmonics that are scaled linearly both in frequency and amplitude. In this mode you have direct control over the harmonicx even though it’s more complex to adjust specific harmonics than in the Morph modes.
The waveform selector is located below the waveform editor.
This is where you choose one of the 16 waveforms to edit. The currently selected waveform is colored differently.
Option-drag (Mac), ctrl-drag (PC): use to rearrange the waveforms.
Command-click (Mac), alt-click (PC) on a non-selected waveform will result in the waveforms morphing from the selected to the command-clicked waveform. This way you can quickly create a whole set of waveforms to edit later.
Option-command-click (Mac), ctrl-alt-click (PC) on an unselected waveform copies the currently selected waveform to the clicked one.
Right-click brings up a context menu to exchange, copy or morph waveforms. Basically the same options as above
Blend < -> Morph
Zebra2 synthesis consists of two different wavetable synthesis principles: GeoMorph and GeoBlend. Geo just stands for geometry regarding the wavefrom display. Additionally there are two kinds of additive synthesis: SpectroMorph and SpectroBlend that can be used to create a waveform.
GeoMorph and SpectroMorph both create sound using Beziercurves, known from graphic and 3d software. If you have created a waveform set (or load the preset Doc waveform morph) and turn the wavewarp parameter on the left the waveform display will split. Zebra2 smoothly interpolates between two waveforms resulting in soft transitions between the waveforms, hence the term “morph”.
The blend modes on the other hand consist of fixed points and the steps between the waveforms are only morphed according to their content and contain their original forms like in traditional wavetable synthesis or vector synthesis.
WaveWarp und Resolution
This dynamic form of synthesis is very CPU intensive, as you may have guessed. After all, the waveforms can be morphed smoothly using the wavewarp paramter.
It is all the more surprising that Zebra2 is still very CPU efficient compared to other synthesizers that calculate their waveforms in realtime. This is achieved using a simple trick: the waveforms aren’t constantly being calculated but at certain intervals. So in effect Zebra2 is a kind of granular synthesizer that uses the grains resulting from the just discussed synthesis.
The resolution paramter determines the length of the intervals between calculations. Higher resolution results in more exact (and faster) transitions from waveform to waveform.
The range of the resolution is between 4 seconds and less than one millisecond. Extreme settings can either significantly increase CPU use (at values closer to 9) or can introduce artifacts such as aliasing (at values lower than 4) with fast pitch modulation.
As a general rule: for faster modulations and more intense pitch modulation the resolution should be at higher values.
Phase
The phase tab allows you to add an inverted version of the current waveform to the signal. Turn up the phase knob to determine the phase of the inverted wave. A sawtooth waveform with an added inverted sawtooth will result in a pulse waveform.
The Sync button activates the oscillators hard sync feature. The oscillator can now be detuned up to 3 octaves relative to its base frequency, while its phase is periodically reset at the base frequency. This effect adds a lot of harmonics and is very great when sweeping the sync offset frequency (Sync parameter) – it’s much like the typical “synthesizer guitar” effect of analogue synthesizers. The main difference here is, while analogue synthesizers needed two oscillators to accomplish this, Zebra does it within each single oscillator.
FX Section
The FX section is another highlight of Zebra2s oscillators!
You can apply 2 FX containing 17 effects algorithms to the generated waveform. There are vast possibilities ranging from crude to very subtle depending not only on the effect but also the waveform.
These effects are calculated right into the waveform. For this reason the resolution parameter is essential for the speed and precision of the result. Higher resolution allows for faster effects modulation. Values of 7-8 should be sufficient for most uses.
In addition to these effects there is a normalize parameter. This works almost like a third effect. Normalize analyzes the level of the generated waveform (not the peak level but the RMS). At 100% normalize will output at 0dB. This is very desirable for some patches to make up for wide amplitudes. However, this can also lead to very loud output in the higher frequencies. Fortunately this is controllable.
- Fundamental:
Adjusts the fundamental sine wave of the sound at pitch played. Ranges from -200% (inverted) to +200% (boost)
- Odd for Even:
Shifts the volume of even harmonics towards uneven harmonics for positive values resulting in more pulse like waveforms, because a pulse wave only contains uneven harmonics.
For negative values the even harmonics become more apparent resulting in a softer more nasal sounds.
- Brilliance:
Boosts or reduces the higher harmonics resulting in brighter or darker sounds.
- Filter:
Behaves like a low pass filter for negative values and a high pass filter for positive values. This filter works on the spectral level and filters at more than 100dB per oactave. It doesn’t feature a resonance parameter but still sounds very wet.
- Bandworks:
This is a spectral bandpass filter for positive values and a bandreject filter (notch) for negative values.
- Registerizer:
Boosts the harmonics that are octaves to the fundamental. This produces an organ-like character
- Scrambler:
This effect is similar to the selfmodulating oscillators of FM-synthesizers: the phase of the waveform is being modulated by itself. This creates sounds with lots of harmonics that can really scream. For warmer sound you woud use it without modulating it. If you like dirty sounds, this is where you get them.
- Turbulence:
Turbulence shuffles the hamronics randomly. This effect is highly dependable on the resolution parameter. It can sound very lively but also very sharp.
- Expander:
Expands or contracts the spectrum. This may sound similar to brilliance if the harmonics are distributed evenly. But try the expander on a spectrum like this:
- Symmetry:
Squeezes the waveform towards the beginning or the end of the waveform. Sounds like pulse width modulation and with a square wave that’s exactly what it is.
- Phase Xfer, Phase Root und Trajector
In these modes a sine wave is influenced by the waveform.
Phase Xfer creates a sine wave and adds the waveform that is being ringmodulated by another sine wave to the phase.
Phase Root multiplies the phase of the sine wave with the waveform.
Trajector adds the waveform to the phase of the sine wave.
All of these can sound very subtle or very noticable. Because of mechanism of each one of them these can sound like the phase distortion synthesizers from the 80s.
- Ripples:
Multiplies the waveform with a sine wave consisting of a variable amount of vibrations. Results in sort of resonant sounds.
- Formanzilla:
Multiplies the spectrum of the waveform with a sine wave consisting of a variable amount of vibrations. Results in nasal sounds.
- Sync Mojo:
Simulates hardsync right in the waveform by contracting the time axis and repeatadly writing the waveform back into the wave memory.
- Fractalz:
Similar to Sync Mojo contracts the waveform and repeats it, however the repetitions are included in the following waveforms resulting in a fractale waveform containing even more harmonics than hardsync.