Fun With Filters

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And so starts the stupendous summer of synths! After establishing the basis of synthesis, the operations of oscillators, and the world of waveforms, we’ll kick off the summer with a look at filters. Like in weeks past, we’ll be using the Minimoog Voyager as our example of how a specific filter works, but first, let’s discuss filters on a broader scope.

A filter in a synthesizer is just like a filter in any other facet of reality: we’re sending a medium through a filter to remove an unwanted part of that medium. In this specific case, we’re sending sound through a filter to remove certain frequencies of said sound. Generally speaking, we’re either trying to remove low sounds, high sounds, or occasionally both.

When you’re trying to remove high sounds, you call it a “low-pass” filter as the low sounds are what are passing through. When the low-pass filter is off, you’ll have a rich, full, bright sound. As you filter more of the high sounds out, the tone will become softer, darker, and more mellow.

By that logic, a “high-pass” filter will allow the high sounds through and will filter out the low ones. Once again, not having a filter will result in the full sound. This time, though, as you filter out the low sounds, you lose a great deal of body and depth, so the sound becomes very nasally and tinny. It can almost have a kind of “mosquito” quality to it.

You can also have a low-pass and a high-pass filter work together to only allow sounds in the middle to come through. This resulting “band” of sound that makes it through the filter is why a combination of these filters is called a “band-pass” filter. Not only does this allow you to control where the highs and lows begin and end, but it also allows you to choose how large of a “band” makes it through.

With the basis of filters sorted, we can put it to practical use with the Minimoog Voyager’s filters. And yes, that’s supposed to be plural! The Voyager actually has two filters that can be set in two different ways: dual low-pass or high-pass/low-pass.

In dual low-pass mode, two different low-pass filters are working together. If you were listening with headphones, one filter would be assigned to the left ear and the other to the right ear. This can allow for some very unusual and unique sounds in that you can essentially have two different sounds going on at once! Since most of the recordings and videos will be in mono, as I am just using one cable to send signal out of the Voyager, you won’t really be able to hear this effect, so we’ll save it for something more in depth further on down the road.

In high-pass/low-pass mode, you have one of each filter. It’s essentially how you create a band-pass filter. You’ll notice that there isn’t a standalone high-pass filter for the Moog. You can get that effect though by letting all the high sounds through the high-pass filter while letting very few low sounds through the low-pass filter. Basically, you’ve made a super small “band” of sound where only the high sounds can get through.

To set these filters on the Voyager (and many synths), you have what’s called a Cutoff Knob. This cutoff point is the frequency at which sounds (high or low) can no longer pass through. The Voyager Cutoff Knob can go from 20hZ to 12KhZ (which is close to the entire audio span of human hearing!).

Right below the Cutoff Knob is the Spacing Knob. For the Voyager, the Spacing Knob acts in two ways. For the Dual Low-pass mode, it essentially acts as the Cutoff Knob for one ear while the main Cutoff Knob functions for the other ear. In High-pass/Low-pass mode, it acts as the Cutoff Knob for the High-Pass filter (which establishes the size of that “band”).

Below that is a particularly interesting knob: the Resonance Knob. When you set the Cutoff Knob, you’re setting it as specific frequency. That frequency can be emphasized by using the Resonance Knob. It often gives the sound a vocal-like quality but can lead to many other interesting effects. On top of that, when you turn the Resonance Knob up to its highest settings, it will emphasize the frequency so strongly that the filter begins to self-oscillate and winds up creating a pure sine wave! This is how I made a sine wave in the last post regarding waveforms, as the Moog oscillators don’t naturally create sine waves on their own.

Then we come to a potentially confusing knob: Keyboard Control Amount. It boils down to this: if you have this knob turned all the way up, it means that as you play higher, the Cutoff Frequency gets higher, too. It’s as though you had an invisible hand turning the Cutoff Knob as you play higher and lower on the keyboard. If you have this knob turned all the way down, the invisible hand goes away and the Cutoff Knob stays the same regardless of the pitch you play. This can be very helpful if you want to make your higher sounds stick out (turn up the knob) or make them more muted and mellow (turn down the knob). Additionally, the use of this knob can really help emulate acoustic instruments in different ways.

Lastly, you come to the one switch amongst all these knobs. It’s just a red switch to go back and forth between Dual Low-pass and High-pass/Low-pass.

With all the knobs and switches explained, let’s end with a video showcasing all of these items back to back using the Dual Low-pass mode:

Next time on Synth You Asked: the power of envelopes and A.S.D.R.!

Harmonics and Waveforms

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Salutations again synth seekers! Last time, we discussed the nature of oscillation and, in turn, oscillators. These controlled oscillations in voltage are translated into definable pitch and sound: slower oscillations result in lower pitches while faster ones yield higher pitches. And if you combine different oscillators, you’ll wind up with multiple notes at once (AKA a chord).

While having actual notes to use is a key staring point, it’d be nice to be able to mold and sculpt these pitches/oscillators as we see fit. Do we want something bright and brash? Or perhaps soft and mellow? Perhaps something hollow and mysterious?

To achieve these different tones/timbres, one of the first variables to adjust is the waveform of each oscillator. We’ll discuss four (technically five) basic waveforms today, but to understand waveforms, you first need to know a little bit about harmonics.

Harmonics are a science unto themselves, so if you really want to dive deep, click here to go wild with math, graphs, etc. For everyone else, I just want to touch on the basics, so you’ll feel more comfortable with the world of waveforms.

In the most basic sense, harmonics are the means by which we create different pitches. A very basic example is to take a string (like on a guitar, violin, etc.) and pluck it. That is the basic fundamental pitch. If you cut that string in half (either by holding it down or literally cutting it), the pitch will now be twice as high (one octave). Other basic fractions of the string will yield different pitches (2/3 the length of the string is a perfect 5th, etc).

Quick side-note #1: if you’d like to know more about intervals in music, check out this post from Master Claset’s Theory Corner!

Additionally (and more practically to our synth studies), harmonics also serve the function of creating different tones and timbres for different instruments.

One of the core elements of this is something called the Harmonic Series, which is shown in the following image:

Harmonic_series_intervalsKnowing exactly what the picture above means isn’t crucial. What I want everyone to take away from this is to imagine that each note can act like a light switch. The bottom note (lower left corner) is always on. That’s the basis of a pitch itself. By turning the other “light switches” on and off, you will generate different tones and timbres. One combination of switches might create a piano tone while another combination might create a trumpet.

In short, different combinations of harmonics yield different sounds. With those ideas in mind, we can get back to the waveforms!

Since we’ve largely been using Moog Synthesizers as a basis for our discussion, I figured I’d refer to my Minimoog Voyager Manual for a brief description of each primary waveform as Moog provides such a concise description of each:

Waveformswhite

Sawtooth: “The sawtooth wave is the richest sounding of the four waves. It contains all of the harmonics, and has a bright, buzzy sound. Sawtooth waves are ideal for brass and string sounds, bass sounds and rich accompaniments.”

Square: “The square wave possesses a hollow sound compared to the sawtooth, owing to the fact that it contains only odd harmonics. This hollow characteristic is ideal for distinctive lead and sustained (pad) sounds.?An interesting aspect of the square wave is that the waveshape can be changed to make the top and bottom parts asymmetrical, creating a pulse wave. By changing the shape of the wave, new harmonics are introduced. Pulse waves are ideal for creating clavinet-like sounds, but are also useful for creating lush pads.”

Quick side-note #2: When Moog refers to changing the shape of a square wave and creating “pulse waves,” these are also known as rectangle waves because you are “crushing” the square shape (see imagine above) into a rectangle.

Triangle: “Like the square wave, the triangle wave only contains odd harmonics, but the levels of the harmonics in a triangle wave are much less. The triangle wave has a soft, slightly buzzy sound that is suitable for high- pitched leads (like a flute) or adding a beefy sub-bass to bass sounds.”

Sine: “The sine wave is the purest waveform of them all. It has no harmonics, so it produces a very pure tone. Because of this, sine waves generally aren’t used as primary audio signals, but are often used to reinforce or enhance other waves. They are also used as modulation sources.”

Quick side-note #3: The Minimoog Voyager I will be using for examples doesn’t make a pure sine wave via its oscillators. I can create one using another means, which I will demonstrate but will save the explanation of that section of the Voyager for another day.

To close today, all of these visual and text descriptions are great but hearing an actual example of these waveforms would be equally if not more helpful. In this video, I’ll have one oscillator on and will cycle through the basic waveforms. The Minimoog Voyager is quite interesting and versatile in that it can “blend” between waveforms, so I’ll move the knob slowly, so you can hear the transformation from one type to another and will pause on each pure waveform. Lastly, I’ll create a pure sine wave via another means (per “Quick side-note #3”).

With our oscillators oscillating and our waveforms morphing, we can prepare ourselves for the world of filters and envelopes!

Lindby Nominations for 2016 FW Weekly Music Awards

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What a craziness! We are so honored to be nominated in multiple categories in this year’s Fort Worth Weekly Music Awards! Below is a rundown for what we have been nominated for:

BEST POP ACT – Lindby!
BEST “OTHER PERFORMANCE” – Nick Spurrier, keys (Lindby), “Trepak (Russian Dance)”
BEST VOCALIST PERFORMANCE – Leon Bridges, Ali Grant (Lindby) “Merry Christmas, Baby”
SONG OF THE YEAR – “Merry Christmas, Baby ft. Leon Bridges and Ali Grant (tanner4105 remix),” Lindby
EP OF THE YEAR – Dashing to the Show, Lindby

And below are some of our friends who helped us out on our projects who were also nominated!

BEST VOCALIST PERFORMANCE – Luke Wade w/ Lindby, “White Christmas”
BEST “OTHER PERFORMANCE” – Mark Smith, Haley Woodrow, Jonathan Woodrow, horns (Lindby), “Spread the Jam”

Woohoo! We are definitely feeling the love at Lindby HQ! Take some time out of your day and vote for something really special…and then vote for Lindby in the FW Weekly Music Awards! HA! But seriously, we would really appreciate a vote in any or all of the categories we’ve been nominated. We have had a blast making everything we’ve been nominated for, and can’t wait to share what we’re working on next! w00000t!!!

Love,
Lindby

PS – In case you missed it, here is the link to cast your vote: Fort Worth Weekly Music Awards 2016 Ballot