diff --git a/README.md b/README.md
index 3fd46d0..cad32fc 100644
--- a/README.md
+++ b/README.md
@@ -54,7 +54,7 @@ the following is the current list of plugins
 - multidim: randomized midi note generator
 - robotuna: automatic pitch correction
 - hysteria: hysteresis nonlinear effect
-- threebandeq: [WIP] 3 band eq
+- threebandeq: 3 band eq
 
 ### basic_gain
 
@@ -134,7 +134,16 @@ turn the values up for loud and distorted. don't set them all to the max at once
 
 ### threebandeq [WIP]
 
-wip, there's nothing yet
+simple three band equalizer
+
+parameters:
+- `low band`: frequency at which the low band ends
+- `high band`: frequency at which the high band starts
+- `low gain`: gain for the low band
+- `mid gain`: gain for the mid band
+- `high gain`: gain for the high band
+
+low band goes from 0hz to `low band`, mid band goes from `low band` to `high band`, high band goes from `high band` to half the sample rate
 
 ## contributing
 
diff --git a/crates/threebandeq/src/lib.rs b/crates/threebandeq/src/lib.rs
index 85fa9ea..bb06c05 100644
--- a/crates/threebandeq/src/lib.rs
+++ b/crates/threebandeq/src/lib.rs
@@ -1,31 +1,122 @@
 #![allow(incomplete_features)]
 #![feature(generic_associated_types)]
 
+// https://www.musicdsp.org/en/latest/Filters/236-3-band-equaliser.html
+
 use baseplug::{Plugin, ProcessContext};
 use serde::{Deserialize, Serialize};
 
 baseplug::model! {
     #[derive(Debug, Serialize, Deserialize)]
     struct ThreeBandEqModel {
-        #[model(min = -90.0, max = 3.0)]
-        #[parameter(name = "gain", unit = "Decibels",
-            gradient = "Power(0.15)")]
-        gain: f32
+        #[model(min = 0.0, max = 48000.0)]
+        #[parameter(name = "low band")]
+        low_band: f32,
+        #[model(min = 0.0, max = 48000.0)]
+        #[parameter(name = "mid band")]
+        high_band: f32,
+
+        #[model(min = 0.0, max = 3.0)]
+        #[parameter(name = "low gain")]
+        low_gain: f32,
+        #[model(min = 0.0, max = 3.0)]
+        #[parameter(name = "mid gain")]
+        mid_gain: f32,
+        #[model(min = 0.0, max = 3.0)]
+        #[parameter(name = "high gain")]
+        high_gain: f32,
     }
 }
 
 impl Default for ThreeBandEqModel {
     fn default() -> Self {
         Self {
-            // "gain" is converted from dB to coefficient in the parameter handling code,
-            // so in the model here it's a coeff.
-            // -0dB == 1.0
-            gain: 1.0,
+            low_band: 800.0,
+            high_band: 5000.0,
+
+            low_gain: 1.0,
+            mid_gain: 1.0,
+            high_gain: 1.0,
         }
     }
 }
 
-struct ThreeBandEq;
+#[derive(Default)]
+struct Eq {
+    // Filter #1 (Low band)
+    f1p0: f32, // Poles ...
+    f1p1: f32,
+    f1p2: f32,
+    f1p3: f32,
+
+    // Filter #2 (High band)
+    f2p0: f32, // Poles ...
+    f2p1: f32,
+    f2p2: f32,
+    f2p3: f32,
+
+    // Sample history buffer
+    sdm1: f32, // Sample data minus 1
+    sdm2: f32, //                   2
+    sdm3: f32, //                   3
+}
+impl Eq {
+    #[allow(clippy::too_many_arguments)]
+    fn process(
+        &mut self,
+        input: f32,
+        lf: f32,
+        hf: f32,
+        lg: f32,
+        mg: f32,
+        hg: f32,
+        sample_rate: f32,
+    ) -> f32 {
+        let lf = 2.0 * (std::f32::consts::PI * (lf / sample_rate)).sin();
+        let hf = 2.0 * (std::f32::consts::PI * (hf / sample_rate)).sin();
+
+        // Filter #1 (lowpass)
+        self.f1p0 += lf * (input - self.f1p0) + VSA;
+        self.f1p1 += lf * (self.f1p0 - self.f1p1);
+        self.f1p2 += lf * (self.f1p1 - self.f1p2);
+        self.f1p3 += lf * (self.f1p2 - self.f1p3);
+
+        let l = self.f1p3;
+
+        // Filter #2 (highpass)
+        self.f2p0 += hf * (input - self.f2p0) + VSA;
+        self.f2p1 += hf * (self.f2p0 - self.f2p1);
+        self.f2p2 += hf * (self.f2p1 - self.f2p2);
+        self.f2p3 += hf * (self.f2p2 - self.f2p3);
+
+        // we subtract from sdm3 because the filter has a three sample delay
+        let h = self.sdm3 - self.f2p3;
+
+        // Calculate midrange (signal - (low + high))
+        let m = self.sdm3 - (h + l);
+
+        // Scale
+        let l = l * lg;
+        let m = m * mg;
+        let h = h * hg;
+
+        // Shuffle history buffer
+        self.sdm3 = self.sdm2;
+        self.sdm2 = self.sdm1;
+        self.sdm1 = input;
+
+        l + m + h
+    }
+}
+
+#[derive(Default)]
+struct ThreeBandEq {
+    l_eq: Eq,
+    r_eq: Eq,
+}
+
+/// Very small amount
+const VSA: f32 = 1.0 / 4294967295.0;
 
 impl Plugin for ThreeBandEq {
     const NAME: &'static str = "basic gain";
@@ -39,7 +130,8 @@ impl Plugin for ThreeBandEq {
 
     #[inline]
     fn new(_sample_rate: f32, _model: &ThreeBandEqModel) -> Self {
-        Self
+        // Default cause we want to start with 0s in everything
+        Self::default()
     }
 
     #[inline]
@@ -47,9 +139,20 @@ impl Plugin for ThreeBandEq {
         let input = &ctx.inputs[0].buffers;
         let output = &mut ctx.outputs[0].buffers;
 
+        let sr = ctx.sample_rate;
+
         for i in 0..ctx.nframes {
-            output[0][i] = input[0][i] * model.gain[i];
-            output[1][i] = input[1][i] * model.gain[i];
+            // frequencies
+            let lf = model.low_band[i];
+            let hf = model.high_band[i];
+
+            // gains
+            let lg = model.low_gain[i];
+            let mg = model.mid_gain[i];
+            let hg = model.high_gain[i];
+
+            output[0][i] = self.l_eq.process(input[0][i], lf, hf, lg, mg, hg, sr);
+            output[1][i] = self.r_eq.process(input[1][i], lf, hf, lg, mg, hg, sr);
         }
     }
 }