I'm not sure how many of you are familiar with Sufjan Stevens, but he's certainly one of my favorite modern singer-songwriters. This article (via Create Digital Music) is about creating live, interactive visuals along with music. I've always felt that well done visuals can really take music to the next level, and this video, created by Deborah Johnson aka Candystation, is a perfect example.

UFO, Black Hawk War from CandyStations on Vimeo.

Deborah currently tours with Sufjan and performs live with him. You can read the accompanying interview here.

Just found this amazing video of a video artist/remixer Eboman remixing found sounds and video simultaneously. This is the kind of stuff we'll all be watching on our fingernail sized ipods in the year 2026.

Indaba Tech Corner Volume 1: Synthesizer Basics

  Hello and welcome to the (tentative) first edition of the Indaba Tech Corner Blog. I’ll be using this Blog to broadcast tutorials related to recording and sequencing music using digital audio workstations (DAWs) like Logic, Protools, Cubase, Digital Performer, and others. Today we’ll start with exploring some basic concepts of subtractive synthesis that should help those of you who are new to synthesizers get started making some very interesting sounds. 

For many of you, you’ll already have some type of basic synthesizer in your repertoire, a simple plug-in in your host program like Garageband (analog or digital basic), Logic (ES1), Protools, or Reason (Subtractor). If you don’t have a synth of any type, but you do have a host program, click here to download Remedy, a free subtractive synthesizer that will work with any DAW that hosts VST or AU plug-ins.

Subtractive Synthesis:

            When you first look at a synthesizer, whether it be an actual physical synthesizer sitting on a desk in front of you, or a rendered virtual synth that exists as a plug-in on your computer screen, your gaze will undoubtedly be met by countless knobs and sliders staring back at you. To the experienced user the layout will be familiar on most types of synths, but to the inexperienced user, the amount of available parameters can be overwhelming. So what do all those knobs do? What can they be used for? The answer to both of those questions is “awesome things”, but before we get to that, let’s start by breaking a synthesizer down into its different components.

The Oscillators:

            Subtractive synthesizers work on the concept of sonic subtraction. When Michelangelo was asked how he could turn a block of raw stone into a sculpture of a lion, he responded “I just cut away everything that doesn’t look like a lion.” In essence, this explains the basic concept of subtractive synthesis; begin with a raw sound wave and cut away what you don’t want in order to shape the sound into what you do want. For Michelangelo, the material was raw, unpolished stone. For us, the material is the raw, unpolished sound created by the Oscillator section of the synthesizer.

            The Oscillators of a synthesizer produce the sound that you will hear come out of the synthesizer by outputting sound waves of different types. You will notice that you can choose between different waves in the oscillator section i.e. sine, triangle, square, saw, etc. (note: these selections may be indicated simply by drawings of the waves)

Each of these waves sound different from one another. You’ll notice by experimenting that sine and square waves are softer and less harsh sounding than saw and triangle waves, though each wave has its own unique characteristics. In addition to wave selection, most oscillator sections of a synth will allow you to mix different oscillators together to further shape your initial sound. Also, the portamento controls in the oscillator section control the time it takes for note to glide from its original pitch to the new pitch.

The Filters:

            Once we have selected our sound wave to work with, the sound travels through the synthesizer to the Filter section. Continuing with the sculpting analogy, if the oscillator is the stone, the filter is a large chisel that carves the stone into its basic shape in anticipation of further polishing.

Filters are used to control the volume of the frequency content of the waveforms. By filtering out certain frequencies, we can change the characteristics of the original sound waves in very dramatic ways. There are three basic types of filters, low-pass, band-pass, and hi-pass. Each works exactly as they say they do; a hi-pass and low-pass filter only lets frequencies above or below a certain threshold pass through to the sound output, while a band-pass filter cuts out sound below and above a certain threshold (a band).

            Below I’ve posted some images of an equalizer. Filters are essentially very simple equalizers with only one band. On the graphs below, the x-axis represents frequency (from 20-20,000 Hz, the range out human hearing), the y-axis represents volume, and the shaded area is the area that is being filtered out. You can see how in each type of filter, the volume and frequency have been affected in different ways.

Low-Pass Filter:

Band-Pass Filter:

Hi-Pass Filter:

            There are two main controls on a filter, cutoff and resonance. Cutoff controls the frequency threshold of the filter, or the frequency where sound gets cut out. In a low-pass filter, cutoff controls the frequency above which no sound passes through, on a hi-pass filter it controls the frequency at which no sound passes below. The Resonance control determines how much the volume of the sound is raised at the cutoff frequency. In small amounts, this creates a frequency bump, or small exaggeration that is good for emphasizing certain sound qualities like bass or treble.  If you turn the resonance control up all the way, many filters have the ability to self-oscillate and will create their own sine wave at the frequency determined by the cutoff. The Filter section also contains knobs or sliders that control the amount of affect the filter has on the sound. These are generally labeled as amount (amt) or envelope (env) knobs.

The Envelopes:

            At this point, we’ve created our basic sound and sent it through the filter section to cut away what we don’t like. When you press a key on your MIDI keyboard now, the sound starts when you press down, and stops when you let go. This is boring, and doesn’t really sound like a real instrument at all. To help make the sounds more interesting, synthesizers have an Envelope section, which is used to further shape the characteristics of the sound.

            When a key is struck on an acoustic piano, or any instrument for that matter, the volume of the sound changes over time. We can break those changes down into four stages, Attack, Decay, Sustain, and Release.

            Attack is the change in volume that happens immediately after the sound begins. Attack time controls how quickly the sound rises up to its maximum volume after being struck. On instruments like a violin, this can take a very long time, whereas percussive instruments have an almost immediate attack time.

            Decay takes place after the attack phase. If you hold a note on a piano you will notice that after it reaches its maximum volume, it lowers a bit and then holds there as long as you hold the key. That fall in volume is the decay phase of the envelope.

            Sustain refers to the stage of the envelope where the volume remains at a constant volume. On a piano, guitar, this is the stage where you are holding the note, and it lasts a different amount of time depending on the instrument.

            Release is the final stage of the envelope, and refers to what happens after you let go of the note. On most instruments the release time is almost immediate, but some instruments (xylophone, triangle, piano with a sustain pedal) have a long release time.

            On your respective synthesizers you’ll notice ADSR knobs. These knobs simply control the time each section of the envelope takes to complete. For the attack section, this will control how long it takes the volume to climb from its minimum to its maximum value, while the release knob will control how long the sound takes to diminish from the sustain value volume to no sound after you release the key.

Since the ADSR on a synth is simply a section that outputs values, these values can be used to control not only volume, but the filter cutoff as well. Most synthesizers have two ADSR envelopes, one to control volume (also referred to as amplitude), and one to control the filter. When dealing with the filter, the ADSR values correspond to the cutoff frequency instead of volume, meaning that the attack time is the time it takes the cutoff to rise from its lowest value to its highest value. By tweaking the volume and filter envelopes independently you can create sounds that range from percussive drum sounds, to slow pad and string sounds that continue to hang in the air long after you let go of the key.         

Most ADSR envelopes also allow you to control the envelope amount. This is the amount of effect the envelope has on the parameter its controlling, which is usually volume or cutoff frequency, though sometimes the envelope can be used to control pitch or other parameters.

Modulation and LFO:

            The modulation section of a synth is the most fun part. Modulation allows dynamic control of synth parameters. On a basic level it is the portion that allows you to control different parameters of the synth without twisting the knobs yourself. In the same way that the ADSR envelope allows you to control the volume or cutoff frequency according to certain guidelines, modulation options let you send value changes to different parameters of the synth.

            The most common modulator on a synth is an LFO, or low-frequency oscillator. We call the LFO a low frequency oscillator because unlike the main waveform oscillators, which are designed to produce sound, the LFO is operating much slower, and is designed to give us a constant oscillating stream of values to control parameters with. By routing the output of the LFO to parameters like pitch, cutoff frequency, or volume, we can create interesting variations to our original sounds.

LFO’s generally give us the choice of what type of wave we are using, the rate of oscillation (how fast its going up and down), and the depth of that modulation on different parameters like pitch, cutoff, resonance, etc. The most common way an LFO is used is to create vibrato sounds. By routing the modulation wheel of a synth to control the LFO’s affect on pitch, we can create vibrato like that of a guitar player or a horn player by holding a note on the synth and playing with the modulation wheel. Every time the mod wheel is used, the LFO begins changing the pitch of notes you are holding. By varying the depth and speed of the LFO, you can create anything from subtle variations in pitch to dizzying helicopter sounds.

Keep in mind that an LFO is simply a portion of the synth that creates a steady stream of output values that oscillate up and down over and over. You can use this stream of values to control any portion of the synth that it will allow you to. You may want to loop a simple sequence while you experiment with routing the LFO to different parameters to see what you can do.

Final Words:

            There are so many different synths available in this day and age. This tutorial is in no way intended to cover everything you should encounter on whatever synth you’re using, but it should help you get a basic grasp of what all those crazy knobs do. Most Indaba users are using some type of host application or DAW to make music with, so hopefully these tutorials will help deepen some users understanding of the tools they have to create music with. If you have any questions or further comments, message me through the site or comment on the blog itself.

Thanks and have fun,

                        Ryan