SeaMoon Funk Machine Bass Pedal Review — The Envelope Filter That Started a Legend

By Igor Odaryuk · Updated October 10, 2026

The SeaMoon Funk Machine first appeared in 1973. Craig Anderton designed it for Seamoon of Berkeley, California, and it was one of the first commercial envelope filters. The original company is long gone, but while the gear industry has exploded with hundreds of envelope filter options at every price point, this little box refused to disappear: in 2020 session bassist Neil Jason brought it back as Seamoon FX, with builder Ben Fulton.

There has to be a reason it came back. I spent a lot of time figuring out what it is.

Rating: 5/5

Verdict: The SeaMoon Funk Machine is an all-analog envelope filter with a slightly rough, vocal character that responds to right-hand dynamics in an organic way. It is less smooth and wide than modern filters, and that is the point. It is ideal for funk and slap players, single-note lines that need vocal character, and studio work needing an authentic vintage envelope filter. It is not for rock bassists who only occasionally want a filter effect.

What Is the SeaMoon Funk Machine?

The Funk Machine is an envelope filter — a pedal that uses the dynamics of your playing to control a filter sweep. When you hit a note hard, the filter opens up with a “wah”-style sweep. When you play softly, it stays more closed and gives you a deeper, more subtle effect.

This type of effect is fundamental to funk and slap bass playing. Think of the bass tones on early Parliament-Funkadelic recordings, or on the classic Earth Wind & Fire albums. That thick, vocal, talking quality in the bass comes largely from envelope filters working alongside the natural attack of the notes.

The Funk Machine is one of the originals. It was designed before boutique effects were a thing, when the options were limited and players needed something that actually worked in a live band context.

The Build

This is a small pedal. Simple enclosure, minimal controls, no digital processing. The original 1970s units had one or two knobs — Depth, and on the later version Frequency Shift. The current Seamoon FX version has Frequency, Depth, Blend and Volume, a preamp toggle and an internal sensitivity trim. That’s it. There is little else to adjust, which initially seems like a limitation but turns out to be one of the things that makes it so usable.

The build quality is solid in an old-school way. Heavy, not delicate. It will survive the kind of abuse that pedals encounter on tour. I have seen original 1970s examples that still work perfectly — and that tells you something about how it was made.

The Sound

Here is what surprised me: the Funk Machine does not sound like a modern envelope filter. It’s not as smooth or as wide in its sweep as something like the Electro-Harmonix Bass Micro Synth or the EBS BassIQ. It has a specific character to it that sounds slightly rough around the edges — but that roughness is the point.

It responds to pick attack and right-hand dynamics in an almost vocal way. The faster you play, the more animated the effect becomes. In a funk or slap context, where your right-hand dynamics are constantly changing, the Funk Machine creates a kind of automatic expression that makes your playing sound more alive.

In the recording I did with it, the thing that kept striking me was how organic it sounded. Not “here is an effect.” More like “here is a bass that is responding to how it’s being played.”

Where It Sits in a Mix

Envelope filters can be problematic in a live band context. They can make the bass sound thin, or push frequencies that conflict with the guitars, or create too much movement when the song needs something solid. The Funk Machine, used thoughtfully, doesn’t have these problems.

The key is the Depth and Blend settings. Keep the depth moderate and blend in some clean bass and it adds character without swamping the mix. Crank everything and you get the full vintage-funk experience — great for solo contexts and funk jams, perhaps too busy for a dense arrangement.

I would recommend it most strongly for: slap playing in a funk or soul context; single-note lines where you want the notes to have more vocal character; and studio work where you want authentic vintage envelope filter sound rather than a modern recreation.

Is It Worth the Price?

The Seamoon FX Funk Machine came out at $199 street, which is expensive for a pedal with four knobs and no digital processing. There are cheaper envelope filters — the MXR M82 is $100 and sounds great. The Aguilar Filter Twin is $160 and has more versatility.

But the Funk Machine sounds like itself. If you want that specific character — that 1970s funk bass sound that was used on the original recordings that defined the genre — there is not another pedal that does exactly this thing. That is worth something to the right player.

If you’re primarily a rock bassist who occasionally wants some filter effect, buy something cheaper. If you are serious about funk and slap bass and you want the real thing, the SeaMoon is worth the investment.

Frequently Asked Questions

How does an envelope filter work on bass?

An envelope filter uses the volume envelope of your signal — how hard or soft you play — to control a filter sweep. When you play hard (high envelope), the filter opens and sweeps upward in frequency. When you play soft (low envelope), the filter stays more closed. The result is a “wah”-style effect that responds automatically to your playing dynamics.

Is the SeaMoon Funk Machine good for beginners?

It works for any level of player but you’ll get more out of it as your right-hand dynamics improve. The pedal responds to how you play — so the more control you have over your attack and velocity, the more expressive the effect becomes. A player with consistent, strong right-hand technique will hear it come alive.

How does the SeaMoon compare to the MXR M82 envelope filter?

The MXR M82 is more versatile, cleaner, and has more modern sound options. The SeaMoon Funk Machine has a specific vintage character that the MXR doesn’t replicate. If you need a general-purpose envelope filter, the MXR is the better value. If you specifically want that 1970s funk sound, the SeaMoon is the one.

Can I use an envelope filter with a pick?

Yes. Envelope filters work with any attack — pick, fingers, or thumb. The character of the sweep will differ depending on how you generate the attack, but the effect functions regardless of technique.