From 823088b629742147f7faff81ac8b164e24c912fb Mon Sep 17 00:00:00 2001
From: Jean Pierre Cimalando <jp-dev@inbox.ru>
Date: Thu, 6 Aug 2020 13:52:49 +0200
Subject: [PATCH] Fix the LPF cutoff

---
 src/sfizz/effects/Disto.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/sfizz/effects/Disto.cpp b/src/sfizz/effects/Disto.cpp
index 4aea5188..9e83856a 100644
--- a/src/sfizz/effects/Disto.cpp
+++ b/src/sfizz/effects/Disto.cpp
@@ -21,6 +21,7 @@
 #include "Disto.h"
 #include "Opcode.h"
 #include "Config.h"
+#include "MathHelpers.h"
 #include <hiir/Upsampler2xFpu.h>
 #include <hiir/Downsampler2xFpu.h>
 #include <absl/types/span.h>
@@ -57,7 +58,11 @@ struct Disto::Impl {
     std::unique_ptr<float[]> _temp8x[2];
 
     // use the same formula as reverb
-    float toneCutoff() const noexcept { return 21.0f + _tone * 1.08f; }
+    float toneCutoff() const noexcept
+    {
+        float mk = 21.0f + _tone * 1.08f;
+        return 440.0f * std::exp2((mk - 69.0f) * (1.0f / 12.0f));
+    }
 
     #define DEFINE_SET_GET(type, ident, name, var, def, min, max, step) \
         float get_##ident(size_t c, size_t s) const noexcept { return _stages[c][s].var; } \