Phasex Core Synthesizer Modules: Oscillator, Filter, Amplifier, Envelope, and LFO


Hi, I’m Sungwon. I grew up in the United States, have been in South Korea the past 9 years and am now living in France for the time being. In this post, I’ll be explaining the most common synth modules: the Oscillator, Filter, Amplifier, Envelope and LFO using the Linux synth phasex.

Core Synthesizer Modules



The Oscillator view in the laptop layout of phasex: four oscillators are available.

The oscillator (or VCO, voltage-controlled oscillator) is essential to any synthesizer as it is the module that generates the sound according to a waveform. The waveform is specified as a parameter and shapes the timbre of the sound. The most common waveforms are Sine, Sawtooth, Square, Triangle and Noise.



The filter module section in phasex. A combination of a low pass and and band pass filter is selected in this screenshot.

Next, the sound generated is further shaped by the filter module. The most commonly-used filter is the low-pass filter (LP in phasex), as synth waveforms tend to be very “bright”. Other common filters include the high pass (HP), band pass (BP), notch and comb. The cutoff frequency and resonance are important parameters in a filter. The cutoff frequency is exactly what it sounds like, the frequency at which the filter decreases the level of the signal. The resonance is the level of the frequency at the cutoff frequency, often used to make a peak at the frequency that allows in additional harmonics to the sound.

Amplifier & Envelope


Next the synthesized sound continues on to the amplifier. The amplifier acts as a preamp for the signal. Amplifiers typically include an ADSR envelope to further shape the sound. ADSR stands for the attack, decay, sustain and release parameters of an envelope.


  • Attack is the time it takes from the time a key is pressed on the synthesizer for the sound to reach the maximum amplitude
  • Decay is the time it takes for the sound to decrease in amplitude from the maximum to the sustain level
  • Sustain is the only parameter that is not a time value, but rather a level. It is the the amplitude level at which the sound is played as long as the key remains depressed (and after attack and decay times).
  • Release is the time it takes for the amplitude level of the sound to decrease to 0 from the sustain level after the key has been released.



The LFO section of phasex includes four LFOs.

The LFO (low frequency oscillator) is another type of oscillator that oscillates in a frequency range below that of human hearing. As such, the LFO is not used to generate sounds but to modulate them, often used to create a vibrato or tremolo-like sound. Common LFO waveform shapes include Sine, Sawtooth Up, Sawtooth Down, Square and Random


Thanks to my fellow students for peer reviewing this assignment!

This is the final assignment in this course. I have learned a lot about sound and music production. While the first few courses seemed very easy, I now feel a little overwhelmed by the breadth of the course. I hope to make time in the future to go through the course again in more depth and begin writing and producing my own music.