PATCHES N PATHWAYS PART 2/3 W. FLORENCE & CHRIS -WAVEFORMS/FILTER/FILTER RESONANCE/FILTER TYPES
PATCHES N PATHWAYS PART 2/3 W. FLORENCE & CHRIS -WAVEFORMS/FILTER/FILTER RESONANCE/FILTER TYPES
TRANSCRIPT
Oscillator Waveform
Florence- So the oscillator waveform can take a number of shapes. We’re going to go through shapes right now. The first one is a sine wave. And you can see that the sine wave has the fundamental frequency that we saw earlier with no harmonic overtones so therefore you get a very smooth and pure sound. The second one is square wave, and we’re going to see that its a buzzier version of a wave with only the odd harmonic overtones and we can use a square wave to build something thats more brassy or a little bit more buzzy sounding, possibly used in video games.
Triangle wave is similar to the sine wave, a little softer and less assuming, You do have some more harmonic overtones so you are getting some ore edge. And triangle wave is great for building flute sounds and making some organ sounds.
The last waveform we have is sawtooth. Sawtooth is the most metallic sounding of all the waveforms. SO we can see it has the most harmonic content and we can use these harmonic overtones to create lead sounds and brass sounds.
Filter
Chris- The filter is the second component in the synthesizer pathway. The filter allows us to remove overtones from the audio signal. Or essentially, the signal created by the oscillator. AS you saw, the oscillator is going to put out these wave forms that have a lot of frequencies across the whole band, and you might want to use them, but natural sounds don't really have them that way, and sounds that are pleasant to us, actually only operate in a few frequency bands. So we use the filter to cut out or accentuate some of the frequencies that are being put out by our synthesizer. Some characteristics of a filter, and some things we might manipulate with it are the cut off frequency, and that is the point at which the filter stops frequencies from passing. And we can also accentuate frequencies using the resonant peak, or Q function of the filter. That allows us to emphasize specific frequencies that happen directly at the point of the frequency cut off. So you can basically, cut off frequencies or you can add frequencies or accentuate them using a filter.
Filter Resonance
Florence- So filter resonance, like Chris said, is used to accentuate the frequencies near the cut off. On this graph here we can see that we get the cut off frequency near where the graph drops off in the first graph, and where we add resonance on the second graph we get a peak which is the increase in resonance around that cut off frequency. And by playing this video we can see that as we’re adding resonance, the amplitude will increase generally.
Filter Types
Chris- So Low Pass Filter is a filter that allows us to remove high frequencies while letting the low frequencies remain. If you look at our chart, our graph, our picture, our image whatever you want to call it- you can see that the white area is the area upon which frequencies are being acted upon. So those frequencies are not being allowed to go through. The blue area are the frequencies that are being allowed to go through. So with this low pass filter, you’re stopping whatever high frequencies you desire that are above the cut off frequency and you're allowing any low frequencies that are below that cut off frequency to go through. And you use this filter to make your sound kinda sound darker, to take harmonic content out, to make your sounds smoother or on any of the wave forms you can approximate the sound of a sine wave by removing all the overtones except for the fundamental.
The high pass filter acts in basically the opposite way of the low pass filter. The high pass filter removes frequencies below the cut off frequency. SO if you look at our image you can see that now on the left side is the white area these are the frequencies that are not being allowed to come through these are the low frequencies. On the right side is the high frequencies, and they are being allowed to come through as long as they are above the cut off frequency. You would use this high pass filter to make your sound seem brighter, or thinner, or even harsher as you remove these lower frequencies you kinda lose the softness and the bass tones of any kind of sound.
The band pass filter is another kind of filter. This allows you to allow only a small band of frequencies through. And nit essentially has two cut off frequencies one on each side. And if we look at our image you can see basically there is kinda this mountain shape, that is the band that is being let through, this blue area. And above, and below that area we’re not letting through. So the band pass filter let’s you kinda accentuate very specific areas of frequency to let you get a kinda honky sound as you're kinda taking our the highs and the lows, accentuating some of the things that we characterize as warmth or nasally sounds.
So the notch or band reject filter is the last kind of filter we’ll talk about. It is basically the opposite of the band pass filter. It’s going to reject a narrow band of frequencies and it essentially has again two cut off frequencies but outside of the cut off frequencies is where it will let frequencies through. So you can see it kinda creates this valley, this dip, in your frequencies that are letting through and you kind of don't use this too much in synths, its actually not found in a lot of synthesizers. Its used more often for recording, and kinda making space for different sounds. But you know, you might find use for it within a synthesizer context.