The Poly800 Moog Slayer, FM-800 and filter mode mods

In standard form, the Korg Poly-800 is a pretty decent synth. Widely considered to be Korg’s answer to Roland’s affordable Juno series, the Poly-800 employed similar digitally controlled oscillators to offer early 80s consumers an alternative to Roland’s budget model.

With six voices, each with two digitally-controlled analogue oscillators, it’s now one of the best choices for vintage polyphonic – or technically paraphonic – analogue on a budget. The biggest weakness is its editing system, with a single pair of up and down buttons used to control all settings, which have to be selected by punching in two-digit codes corresponding to each parameter (a similar system to the slider-based setup used on synths like the Yamaha DX7 or Roland Alpha Juno).

Plenty of owners are willing to accept that editing the 800 is just a bit fiddly and slower than a one-knob-per-function setup, but that that’s part of what makes it so much more affordable than its stablemates such as the PolySix. Others choose to use a MIDI controller to speed things up. That certainly makes the Poly800 quicker to program, but a few simple mods make the synth much more hands-on. The most popular are the so-called Moog Slayer mods, which add knobs for filter cutoff and resonance to the Poly800’s front panel. The name should probably be taken with a pinch of salt, but there’s no doubt that the filter really comes to life with the additional controls.

Other popular and relatively straightforward hacks include the FM800 mod (which adds frequency modulation of the filter cutoff), switches to flick between 12dB and 24dB filter modes, and external audio inputs. All are fairly simple to achieve for the competent DIYer or available from modding services like If those mods sound far too basic and you really want to take the Poly800 to the next level, no problem: the HAWK-800 software upgrade kit adds a huge range of features, including vastly extended MIDI support. The additional AtomaHawk option also allows you to control the Moog Slayer, FM-800 and filter mode switches via MIDI, as well as storing their settings to the memory slots as part of patches.

Given the low prices of second-hand units and the relative simplicity of the Moog Slayer and FM-800 mods, the Poly800 makes an ideal candidate for newcomers to synth modding, but it’s also more than possible to take it to extremes. Just ask Ethan Halsall, whose FrankenKorg 800 incorporates all the usual mods plus a built-in Alesis Nanoverb, a Toshiba laptop and more…

16th June, 2015


  • What about the Mute Synth II?

  • Great read. Thanks.

  • The extensive envelope control on the x0xi0 is really the defining feature…but all in all, a wonderful, wonderful mod that transforms the x0xi0 into something else entirely…

  • Well, going back, the E! and and SuperMAX for the Yamaha DX7 are pretty amazing, but maybe not so much for your audience. The SCI Pro One TurboCPU+MIDI might be though.

  • What about Europa for Jupiter-6 and Gligli for Prophet-600? They’re great inexpensive massive upgrades. Gligli is even free.

  • There is no link for the Tubbutec mod in the article. Here is the link:


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