As a digital signal is generated, it is then sent through various processors pre-determined by the parameters set on a synthesizer as far as source/destination routing. These processors are referred to as modules. The standard group of modules found on most synthesizers include the oscillator, a filter, an LFO, pitch control and a global panel. As you encounter various synthesizers, you will notice that each model is a unique variation of modules. With digital technology, routing is far more flexible and efficient as it requires no physical patching of cables to divert signal flow.
Assuming all modules are enabled in sequence we will follow the oscillator with pitch control, the filter then finally the LFO.
The oscillator generates a signal based on a pre-determined wave-shape and pitch. The signal is then routed based on active modules and the routing algorithm selected (series or parallel). As previously discussed, the routing of oscillators will set the foundation of the synthesizers signal flow. For more information on signal flow refer to Digital Synthesis Basics #001 Oscillators and Routing, click image!
Pitch control allows you to not only set a neutral pitch but allows sweeping of pitches via envelope modulation. Many different sound types have pitch sweeps based on the type of instrument itself. Drums have a pitch down sweep component to them while a water droplet effect creates a pitch up sweep. Understanding resonance in acoustic sounds will help determine the placement of pitch sweeps.
Use tools in music production to accurately determine and generate tuned pitches whether sweeping through or scrolling towards a target (portamento).
Filter operation is standard in music production. The shape determines the band of frequencies to be removed providing a particular character. Filters will often allow you to select circuit types that may be modelled after analog synthesizers to provide states of ‘overdrive’ which in turn introduces distortion either by soft/clipping, limiting or wave-shaping. For more information on filter functionality refer to Music Production Series #005 Filters, click image!
Unlike the oscillator, pitch and filter, the LFO is a source of modulation meaning it can automate parameters found within the synthesizer and its modules.
LFO stands for low frequency oscillator. It has all the capabilities traditional oscillators carry, yet it is unable to ‘oscillate’ fast enough to produce a frequency high enough for our ears to perceive. Our human range of hearing is typically defined as 20Hz to 20kHz. LFO’s typically run at a frequency of less than 20Hz. This enables the signal of an LFO to be a great source for modulation.
Having a free running LFO as a modulation source as opposed to simply creating the automation manually is far more reliable and efficient as you know you’ll always have an active source of modulation.
The selectable wave-shapes of the LFO allow for creative modulation types such as smooth movements, percussive rhythm, randomness and large sonic swells. Step sequencing is also easily achieved by utilizing the square waveform.