¡Edwardo Y Los Asesinos De Boyd Arroz!

Hello again!
     It took me longer than I anticipated, but here is the performance of Ed Cuevas and I from just before Labor Day weekend. I hope you like it. At the end, Ed really gets into it and starts rocking out on his guitar pedal.




...My mistake in "Player Piano" was my failure as a futurist. I did not foresee transistors, and so imagined that super computers would have to be huge, with bulky vacuum tubes taking up a lot of space. -Kurt Vonnegut in "Letters"

Sampling, Additive Synthesis, and a Man Named Fourier

            What is the difference between a sampler and a synthesizer? Sometimes depending on the sampler, not much. A sampler instead of having an oscillator to generate its signal has previously recorded sounds that are used, and in some cases modified just like a synthesizer. So some samplers are in fact synthesizers.

            My next question that I have for myself is, if synthesizers can create whatever sound you want it to, why do you need samplers? The answer, “Myself”, is because while synthesizers can create a vast number of sounds, they do have their limitations. Take Additive Synthesis for example. With Additive Synthesis, you can create any sound you want by adding sinusoidal waveforms on top of each other to create a lifelike sound such as a piano. The difficulty lies in the fact that complex waveforms such as our voices, a piano, or a bird singing, have an infinite number of harmonics, or for this examples sake, sinusoidal waveforms.  

On a side note, it was Joseph Fourier that figured out that all complex waveforms could be broken down into sinusoidal waveforms. Science is fun.

This representation of additive synthesis shows
just 3 waveforms. Now just imagine adding 100
more to get closer to an accurate representation.
And suddenly the redundancy of the matter
sets in.

            A complex waveform, such as a note on a piano, has what is called the fundamental, or the lowest frequency heard that acts as the base for all the rest. On top of that fundamental, there are harmonics, or partials (harmonics are whole-number multiples of the fundamental, while partials are any frequency within the sound’s spectrum) that stack up and create the unique sound. By adding all these partials together and varying the amplitude of each we can create a fairly close representation of the sound.

            Additive synthesis has its limitations, and that is it can be costly to keep buying oscillators, envelope generators, and amplifiers for each sinusoidal waveform. New technology such as virtual instruments make the stacking of a large number of waveforms possible, and only are limited by your computer’s processor, but it takes time and it is not the most enjoyable form of synthesis (who knows, you can be weird and like it, I wont judge you…). Each time you stack the sinusoidal waveforms and get an accurate representation of the sound, you just created one pitch; now if you want to mimic an entire piano, you have to do it for each individual note (I’ll see you in a few years when your done).

            That is where samplers come into play. Samplers allow you to take a recording of a sound, such as a piano note, and play it. By doing this, instead of having to go buy an expensive piano, you can get a fairly accurate representation of just about any piano. While the more expensive sampling instruments do cost you a hefty sum of money, it is nowhere near as much as that grand piano you just sampled costs.

            Piano sounds are just one option, samplers allow you to load any sound you want into them. They give the performer access to sounds and instruments that they 1) would otherwise not be able to play or have access to and 2) not be able to or want to purchase. A world of possibility lies within the world of synthesis and sampling, you just have to take the time to find it (hopefully not with additive though, but again, I’m not judging you…).

A caption depicting
the first 6 harmonics of
a sound.

A spectrum analyzer depicting the frequency content of a sound. 

...My mistake in "Player Piano" was my failure as a futurist. I did not foresee transistors, and so imagined that super computers would have to be huge, with bulky vacuum tubes taking up a lot of space. -Kurt Vonnegut in "Letters"

Subtractive Synthesis: Under a Microscope

            As I discussed last week, Subtractive Synthesis consists of a VCO that generates a signal, a VCF that filters out some of the waveform’s frequencies, and a VCA that amplifies the signal. However, there are other components that help shape the sound, and also, control each of the parameters.

The CV lasts as long as the envelope generator
tells it to. The Trigger is a quick pulse,
initiating when the key is pressed. The gate
lasts as long as the key is being pressed.

            In analog synthesis there are three basic control parameters: the control voltage, the gate signal, and the trigger signal. A control voltage is a variable voltage that is commonly used to determine pitch, or the frequency of the key pressed, and it can also be used to control any other number of parameters through external patching or internal patching (depending on what type of synthesizer you have). A gate signal is a steady voltage that denotes a key being pressed, starting when the key is pressed and ending when it is released. Lastly, a trigger signal is a quick pulse of voltage that is used to start an event such as a key press.

            When these signals are initiated either by a keyboard or other source, it is sent to an envelope generator that determines the path of the signals. Gate and trigger tell an envelope generator when to initiate. Commonly, attack, decay, sustain, and release (ADSR), of the envelope generator starts the attack upon the initial gate and ends when the trigger message is completed allowing the envelope generator to finish the release.

            Another feature that many Subtractive synthesizers have is the LFO (Low Frequency Oscillator). This feature is not common on many older Subtractive synthesizers due to the fact that their oscillator’s frequency range went quite low, lower than the range of human hearing allowing them to function much like a LFO (one oscillator was just designated to act as the LFO). LFO’s when added to the mix, lend certain qualities to the sound such as vibrato when it controls the VCO frequency, and tremolo when it controls the volume of the VCA. LFO’s can also be put on the VCF to control any of the parameters to create a richer sound.

            Other controls such as pitch bend (it bends the pitch up and down, but don’t quote me) and modulation (is assignable, and can control whatever you assign to it) use a variable voltage wheel to alter the parameters. These functions are usually located next to the keyboard, if it has one, and allows the user to adjust a wide range of performance parameters without having to go tweaking knobs on the synthesizer while they are playing.

            Some keyboards also have various other performance modifiers such as aftertouch that allows the user to change an assignable parameter by pressing the keys harder or down again without having to fully release them. Then there are other modifiers that come separately that we will not get too in-depth about such as a sustain pedal, expression pedal, and a breath controller, that interestingly enough allows you to mimic the expression of wood wind instruments.

            Again, this is not a complete rundown of Subtractive Synthesis, but rather a beginning or introduction. Each synthesizer is different, but they all share most of the features that I have described. For a more in-depth look, I will post a video of myself going over my Paia Fatman in the coming weeks (so keep following).

A basic block diagram depicting the signal flow
of a Subtractive synthesizer. With the the keyboard
sending the three control messages, a VCO,  VCF,
 VCA, and multiple envelope generators and LFO's. 

...My mistake in "Player Piano" was my failure as a futurist. I did not foresee transistors, and so imagined that super computers would have to be huge, with bulky vacuum tubes taking up a lot of space. -Kurt Vonnegut in "Letters"