Thursday, August 28, 2014

Usage of the 5 most important synthesis modules

Hello there. I am Jonie Lim from Malaysia. This is the final assignment from Introduction to Music Production on Coursera. For this week, I am choosing the topic of explain the usage of the 5 most important synthesis modules.

Let me further break these 5 modules into 2 categories, the primary modulation and the secondary modulation. The oscillator, filter and amplifier are of primary modulation. They work directly on the sound that we will hear. The secondary modulation includes the LFO and envelope, which will modulate the primary modulation during the audio signal manipulations.

Primary modulation

Oscillator is also known as VCO, voltage controlled oscillator. The main functino of this module is to create the sound. It creates the sound with a timbre based on the waveform selected in the synthesizer. Sine wave is normally giving a single frequency range, triangle and square waveform will have the fundamental plus the odd harmonics, while sawtooth waveform will gives fundamental plus odd and even harmonics in the timbre.

Filter, or also known as VCF (voltage controlled filter), is used to shape the spectrum of the generated sound. This would determine how the generated audio signal sound, for example to sound like a tuba or a flute. This module often under the control of an envelope or LFO. The filter can be of low pass, high pass, band pass, notch or comb filter.

Acoustic filters.svg
"Acoustic filters" by Acoustic_filters.png: Mike.lifeguard
derivative work:  ¡X Mike.lifeguard - Acoustic_filters.png. Licensed under Public domain via Wikimedia Commons.

Amplifier, or VCA (voltage controlled amplifier, shape the volume of the sound signal. It amplifies or attenuates the signal before it is passed to the external. The gain of VCA can be controlled by LFO or envelop generator too.

Secondary modulation

LFO, low frequency oscillator, is used to modulate the sound with a very low frequency signal, which is normally out of the human audible range, 0Hz - 20 Hz. Similar to oscillator of the primary modulation of a synthesizer, the signal can be of any waveform. It can create vibrato effect on the sound.

Envelope provides the envelope modulation to shape the volume of the produced note. The envelope is formed by 4 parameters, attack, decay, sustain and release. All of these parameters are in time domain, except the sustain is based on the amplitude.

ADSR parameter.svg
"ADSR parameter". Licensed under CC BY-SA 3.0 via Wikimedia Commons.

These are the 5 important modules in a synthesizer. Thanks for your time reading this. I am still in progress to identify each of these elements and the controls and how they work in the software that I have. Hopefully, I can identify them soon. Have a great day! :)

Thursday, August 21, 2014

Flanger vs Phaser

Hello there! I am Jonie Lim from Malaysia. This is the 5th week assignment for Introduction to Music Production on Coursera. This week topic is very tough for me, I'll try my best to explain how short delay effects, i.e. flanger and phaser function.

Firstly, as usual, let's listen to the original guitar sound which I have pre-recorded. Warning: I am not a good guitar player. :P

My workspace.

In order try to show the difference between the flanger and the phaser, I have the parameters set similarly.

Flanger settings

Phaser settings

Note that I have both set to the highest intensity to make sure the effect is significantly audible. Next, I set both speed to 0.5Hz. This is the low frequency used to modulate the signals. The flanger can have the feedback set to be inverted or normally here. Since the phaser cannot have it set inverted, thus I have both of them set to 50%, and the feedback of flanger is set towards normal feedback.

Next, let's look at some technical aspects of the 2 audio effects.

A flanger is an audio effect that mix 2 identical signals together, with one of the signal is slightly delayed, and it gradually changing across time, which is 0.5Hz in the sample here. It is normally controlled by a LFO (low-frequency oscillator). It produces notches like a comb filter if the signal is observed under frequency spectrum. The audio effect sounds more harmony and distributed evenly across time. This is due to the delay is applied to the signal equally.

Building block of a flanger

Audio effect after applying the flanger plugin:

A phaser on the other hand is a special effect depends on the DAW or the gadget maker to set the notches across the frequency spectrum. Most of the time, a phaser have only a few notches across the frequency spectrum. Similarly to flanger, it is also modulated by a LFO so that the position of the notches continuously move across the frequency spectrum. The audio effect of phaser sounds more synthetic and more significant in sweeping between left and right track on the same settings. A phaser is based on a chain of all pass filters, which all of these filters will be modulated by a low frequency delay. Thus, the output of the phaser block has a non-linear delay mixed with the original signal.

Building block for a phaser

Audio effect after applying the phaser plugin:

This week's assignment, is the toughest one so far. Did quite a number of readings and re-watched the lecture videos a few times, and find myself still digesting this big topic. Guess it would be a life-long learning process. I used flanger in one of my recordings previously, I didn't literally "know" that, until doing this assignment. The only one reason I applied that effect to the guitar track was... I played it badly, and this effect seems covered the weakness a lot. :P Anyway, you can check it out at : 碎心:

Thursday, August 14, 2014

Noise Gate

Hi! I am Jonie Lim from Malaysia. In this week 4 assignment, I would like to dive in the noise gate plugin. I have a very simple "studio" setup, a MacBook, itself. I don't have a mic or special room to do recording, thus accoustic noise is my #1 concern in recording. In this blog post, I'll be using one of my previous recordings to demonstrate how to use the noise gate. I am using GarageBand 5 for this assignment.

This is the audio waveform from the small purple recording that is splited and copied out from the original recording. To hear the contrast, the effects or plugin that I have put on that track are removed.

This is the original recording sounds like. You hear a "click" sound at 0:04 going into 0:05, and also notice the significant noise right after the singing phrase.

Look at the audio waveform, the "click" sound is highlighted. To get rid of the noise and also the unintentional "click" sound, we can use a noise gate plugin to filter them. As we know, our recording sound is normally much louder or has the higher amplitude than the noise. In this case, we can set the noise gate at the threshold where it is higher than the noise, but below the sound of interest, which can be singing or instrument playing.

Due to there is no other view in GarageBand 5 to adjust the threshold accordingly, thus this is required to do manually by listening. In this example, I set the threshold to -36dB.

Below is the mixed output.

OK, that's all for this post. I hope you can hear the difference between the original, untouched recording and also the effect of the noise gate plugin to that recording.

In case you are interested in listening the whole song, you can visit the YouTube page at :

Note, this was recorded prior of this class, and noise gate was not applied. However, it might not so significant, as the singing and instruments are louder than the noise, a lot, as a whole. I normally try-and-error to apply the preset plugin to get the sound effect that I wanted. Next time, I'll try to use the noise gate to eliminate the unwanted noise. :P

Hope you enjoy reading! Cheers!

Thursday, August 7, 2014

Audio effects

Hi! I am Jonie Lim from Malaysia. In this blog post, I would like to talk about the audio effects. This would be my 3rd week assignment for Introduction to Music Production.

Basically, there are 3 major categories of audio effects, which related to the 3 properties of sound. I am going to take a plugin for each category, and explain how these plugins work in GarageBand 5.

I have recorded a singing on 4 notes and export to mp3 with no audio effect being applied.

You can listen it here.

1. Dynamic Effects

Dynamic effects play with the amplitude of the sound. One of the plugins that put manipulate amplitute of the sound is compressors. Basically, a compressor would "squeeze" an audio signal when it rises above a specific threshold level. In GarageBand, it would then take the setting of ratio for the strength of the compression, attack setting for when the compressor should react to the signal breaching the threshold, and then the gain setting to set the loudness of the effect to the audio signal. See the screenshot below.

I put on the effect to the audio earlier and mixed to mp3 again. Here's what you will get by applying the above setting to the original audio signal.

To me, the effect is very mild. One way to "observe" the differences, is by the visualization of the mp3 file playing on the media player.

2. Delay Effects

Delay effects play with the propagation property of the sound. It provide the sense of space of the audio signal in the mix. One of the plugins for this is flanger. A flanger mixes a delayed same audio signal and the original signal together. Here's the setting I have applied to flanger to the original audio signal.

The intensity setting is for how much the flanger effect applied to the mixed. The speed setting is for how much latency the "new" audio signal will be mixed to the original signal. The feedback setting is for how much feedback is applied to the modulated signal.

Observed the difference of the following mixed audio with the original audio.

3. Filter Effects

Filter effects control the impact on the timbre/frequency of the sound. One of the plugins for this is Band Pass filter. It passes frequencies within a certain range and attenuates frequencies that is outside of that range. Let's see the example that I applied to the original recording.

I set the bandpass filter to ~2.7kHz, and let the attenuations happen gradually around that frequency.

Hear the impact of applying this plugin to the original recording. You may find out the "sound" has been "cut" and feel incomplete. It sounds like the audio signal has been transmitted to the loudspeakers for output. :)

In summary, I have prepared the table below.

Audio effect Sound property Audio plugins Effect/Usage
Dynamic Effect Amplitude Compressor Squeeze the audio signal when it is above a threshold value, which would reduce the signal dynamic range. This will results in a "flattening" of the sound.
Limiters Boost the signal before the threshold and limit the audio signals that is out of the threshold.
Expanders Amplify or attenuate the audio signal. Stereo expander can create a surround effects which can enrich the stereo field of a mono signal by creating spatial effects.
Gates Only allow a signal to be heard if it exceed a specific volume threshold. This can be used to silence a constant low noise floor from a signal.
Delay Effect Propagation Reverbs Apply echo effect to give a sense of the room size effect.
Delays Apply delay effect on the original signal.
Phasers Create peaks and troughs in the frequency spectrum and these effects are vary over time to create a sweeping effect on the audio signal.
Flangers Mix a delayed signal to the original signal.
Choruses Mix different pitched of the original signal.
Filter Effects Timbre (Frequency) High pass filter Passes high frequency signals and attenuates frequencies lower than the cutoff value.
Low pass filter Passes low frequency signals and attenuates frequencies higher than the cutoff value.
Band pass filter Passes signals for frequencies within a certain range and attenuates frequencies outside of the range.
Equalizer Boost or cut each frequency to control the frequency response characteristics.

I read the feedback from the peer evaluators, and really feel appreciated on the comments given. Hope I improved on my assignment this week. Thanks for spending time to read this. I hope you enjoy this. :)