Low-frequency oscillation A low-frequency oscillator (LFO) 

generates an electronic signal, usually below 20 Hz. LFO signals create a periodic control signal or sweep, often used in vibrato, tremolo and other effects. In certain genres of electronic music, the LFO signal can control the cutoff frequency of a VCF to make a rhythmic wah-wah sound, or the signature dubstep wobble bass.   #low-frequencyoscillator #lfo Envelope Main article: Envelope (music)  Schematic of ADSR Envelopes control how sounds change over time.

 They may control parameters such as amplitude (volume), filters (frequencies), or pitch. The most common envelope is the ADSR (attack, decay, sustain, release) envelope:[7]  Attack time is the time taken for initial run-up of level from nil to peak, beginning when the note is triggered. Decay time is the time taken for the subsequent run down from the attack level to the designated sustain level. Sustain level is the level during the main sequence of the sound's duration, until the key is released. Release time is the time taken for the level to decay from the sustain level to zero after the key is released. LFO   #Synthesizers generate sound through various analogue and digital techniques. Early synthesizers were analog hardware based but many modern synthesizers use a combination of DSP software and hardware or else are purely software-based (see softsynth).

 Digital synthesizers often emulate classic analog designs. Sound is controllable by the operator by means of circuits or virtual stages that may include:  Oscillators typically produce waveforms (such as sawtooth, sine, or pulse waves) with different timbres.[7] #Lowfrequencyoscillators (LFOs) produce waveforms used to modulate parameters, such as the pitch of oscillators (producing vibrato).[7] Voltage-controlled filter (VCFs) – "shape" the sound generated by the oscillators in the frequency domain, often under the control of an envelope or LFO. These are essential to subtractive synthesis. Envelope generators – provide envelope modulation to "shape" the volume or harmonic content of the produced note in the time domain with the principal parameters being attack, decay, sustain and release. 

These are used in most forms of synthesis. ADSR control is provided by envelope generators. Voltage-controlled amplifiers (VCAs) control the volume or gain of the audio signal. VCAs can be modulated by other components, such as LFOs and envelopes.[7] After the signal generated by one (or a mix of more) VCOs has been modified by filters and LFOs, and its waveform has been shaped (contoured) by an ADSR envelope generator, it then passes on to one or more voltage-controlled amplifiers (VCAs). A VCA is a preamp that boosts (amplifies) the electronic signal before passing it on to an external or built-in power amplifier, as well as a means to control its amplitude (volume) using an attenuator. The gain of the VCA is affected by a control voltage (CV), coming from an envelope generator, an LFO, the keyboard or some other source.[51] Filter weki