Subtractive Synthesis 102 – Filter and ADSR

Welcome back…for those of you who don’t know, this is part 2 of our intro into subtractive synthesis. If you missed the beginning go here now.

In the last post, we covered a little about subtractive synthesis and we started to explore the idea of how tone generation works. This week we are gong to take the tone we made in part 1 and shape it further….


Filters are the third part of the equation of basic tone construction, the other two being wave-tables and volume envelopes. This is one of the most fun parts of synthesis. There is also an added bonus of being able to transfer this knowledge elsewhere in the audio production environment.

So what do they do?

They filter out a signal so you can’t hear it.

Core components of the filter:

DB per octave (roll off rate): This is the steepness of the curve. The steeper the curve the larger the number. The higher the roll off rate, the sharper the filter. So a 6db per octave would reduce the signal by 6db every musical octave where as a 24db per octave filter would reduce the signal by 24db every musical octave

How steep you make the roll off rate will depend on what you are trying to achieve but a basic rule of thumb is:

The steeper the curve the more unnatural it will sound.

Next,  the filter knob is another knob which you might not know but will have definitely heard of. The ‘Resonance’ controls the filter point volume. Crank it up and watch the filter point get really loud using this.

Classic Acid House.

The four horseman of the filter:

LP (Low Pass):
The ‘Low Pass’ allows only sounds below the filter point to be heard.

HP (High Pass):

The ‘High Pass’ allow only sounds above the filter point be to heard.

BP (Band Pass)

‘BP’ is a combination of the LP and HP.  This allows only the sounds in between the two filters to be heard.

LP + HP = BP

Notch (Band-Reject)

The ‘Notch’ is the opposite of the band pass. It allows only the sounds outside of the area to be heard.

Invert the BP…

Get your hands dirty:

Load up your project with your 1 bar loop.

Add a band pass filter

Just move around til you find something cool

Take your volume fade, click 4 nodes. These will be our ADSR envelope.

Place them like so.

Use additional nodes to adjust to taste

Adding bit crusher changes the 2nd sound just touch. So it feel more human

Finally add a reverb because we can.

No rule just play, You can use the volume curve on your channel to edit decay if you’ve gone for a long decay time.

Awesome, you have just created your first sound.

From here you can render it out and we can move it into the sampler.

“What about the filter ADSR curve?”

ADSR envelope can be applied to the filtered section as well. Instead of the sound being shaped over time, the filter movement will be shaped instead.

I’m going to let you experiment here.

Move back to the synth, initialize it and move through the steps: tone, filter then ADSR and create another patch.

IDEAS: Things to try out: make an identical to the volume ADSR,  an opposite and an inverted. Then go for your life.

That’s it for this week, stay tuned next we are going to place our sound in our sampler and creating a unique instrument.

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About Braydon Zirkler

Currently based out of Melbourne. I'm dividing my time up between this blog, teaching, a radio show that's in the works and working on a live performance project with physical theatre performers. Get in touch here:
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One Response to Subtractive Synthesis 102 – Filter and ADSR

  1. Pingback: Subtractive Synthesis 103 – Modulation and what is an LFO? | Blind Man Bass

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