The synth now runs in both standalone mode and as an audio unit inside a host application. Audio Unit version 3 brings iOS closer to the OSX/Windows music production model, by allowing plugins to be chained together to form advanced processing chains.
The synth uses a synthesis technique called wavetable synthesis. This form of synthesis adds an extra dimension to synthesising single waveforms, with the focus on how sound evolves as the waveform changes over time.
The synth has 2 oscillators which generate the sound and have controls for modifying the different synthesis properties. Each of the controls on the oscillators can be modulated to automate changes over time.
The synth is polymorphic, which means multiple keys can be active at once, with each key press using a voice.
This brings us to the modulation sources, the key to unlocking the synth.
First off, the wavetable index property is the core property, as it controls which waveform is being synthesised and moving through the wavetable causes the oscillator to change its waveform, creating evolving and complex sounds.
The synth contains 2 types of modulation sources. ADSR envelopes and LFOs. ADSR stands for Attack/Decay/Sustain/Release, which mimics the way a piano key generates sound. There is the initial key press and the time it takes for the sound to reach its maximum amplitude. There is then the time it takes the sound to reach its sustained amplitude as well as what that sustained amplitude is. Finally there is the release time which is how long the sound takes to stop after the key is released. Each of the time based parameters, Attack, Decay and Release are millisecond based.
The synthesiser's ADSR envelopes are hard wired to the oscillators amplitudes, one for each oscillator.
LFO stands for Low Frequency Oscillator, which is essentially an oscillator that runs at a far lower frequency, i.e. far less cycles per second. LFOs work well for modulation because we can modulate controls at speeds which result in musical sounds.
To enable modulation, drag the link from the source and drop it on one of the oscillator controls. This will create a source->destination link and the modulation can be accessed in the mod matrix view. Modulation on a control can be overridden allowing multiple sources to a single destination. Each new override will disable the current link, keeping it linked. Links can then be enabled and disabled as needed in the modulation matrix view.
On to the effects. The synthesiser has a signal flow from the oscillators through the filter delay effect module, through a filter and finally through a reverb module. This runs from top to bottom on the user interface on the right of the oscillators.
The filter delay module is a combined effect containing a bandpass filter and a delay line, split into 3 paths, left, centre and right. There is a filter and delay line for each path. This flexibility allows sculpting of the signal with powerful control over each path's setup. The bandpass filter can be disabled either by double tapping the filter grid or via the on/off button, accessible via the show more controls button.The same is possible for the delay line, which can be enabled or disabled, per path.
Next is the filter module, which is a general filter that can change filter type. It has cutoff, resonance and gain properties, when working with shelving filters.
Finally the reverb module provides excellent depth and space to the mix, with selectable presets.
Let's move on to the Wavetable Creator overview.