Fat Line Bass Patch

Korg Fat Line Bass patch on any synth (Synthwave sound design)

bass sound design synthesis


The Fat Line Bass is a patch from the Korg Polysix synth which is used on tons of Synthwave tracks.

It may just be the quintessential Synthwave bass sound due to its versatility and popularity.

In this video, I’m going to show you how to recreate it on any synth VST, while using the free synth GR-8 by Phuturetone as an example.

Let’s get to it.

For this recipe, we’ll need a synth with at least 2 oscillators and unison capability with a minimum of 6 voices.

Here are the parameters and values I copied for the Fat Line Bass preset from my Korg Polysix vst.


  • Oscillator section
    • Osc 1: saw
    • Osc 2: Square, 1 octave below Osc 1
  • Filter section
    • Cutoff: 30%
    • Resonance: 9%
    • Filter amount: 50%
    • KBD Tracking 30%
  • Envelope section- shared for filter and amplifier
    • Attack 0
    • Decay 30%
    • Sustain 0
    • Release 30%
  • Voice Section
    • Modulation: Velocity to cutoff 10-20%
    • Unison mode: 6 voices
    • Unison spread: 80%
    • Analog or drift: 10%

Before we start, be aware that because every synth is different, just copying the parameter values from one synth onto another will not work most of the time.

So what we’ll do is first copy the settings and then tweak the patch by ear to get it as close as we want it.

  1. We’ll start with an initialized GR-8 patch
  2. We’ll now set OSC 1 to saw, Osc 2 to square/pulse and adjust OSC 2 pitch so it is an octave below OSC 1. Let’s set the Mix knob to 50/50
  3. Next up is activating Unison, setting Detune to 0 and the Spread to 80%
  4. I find it easier to program a specific sound like this while having a realistic pattern going on in the background so let’s play what we have so far
  5. The Polysix has only one envelope generator for both the filter and amp, so we’ll set the Filter to use envelope 2 with this slider. Now we can control both amp and filter with the same envelope
  6. Set the attack to 0, Decay to 30%, Sustain to 0 and Release to 30%
  7. Let’s head over to the Filter section and set the Low-Pass slope to -24, cutoff to 30%, Resonance to 9%, key Tracking to 30% and Envelop Amount to 50%
  8. It doesn’t sound like the Fat Line Bass just yet but that’s to be expected since no two synths will sound exactly the same.
  9. Let’s play with the decay, filter amount and Cutoff to get it in the ballpark
  10. As icing on the cake, we can enable velocity to Filter Cutoff modulation so notes with high velocity will make the filter open up in order to provide accents and movement to the bass line. The MIDI pattern we’ve been using has already been programmed with high velocity notes


The Fat Line Bass is a relatively simple patch to program and GR-8 can get us really close. If you want THE sound of Synthwave bass in your productions, then look no further and follow what I’ve shown you in this tutorial. But don’t forget to experiment with minor alterations and to make it your own.

Have fun!

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