diff --git a/filter_moog_f32.cpp b/filter_moog_f32.cpp
index 1d488aa..813ea4e 100644
--- a/filter_moog_f32.cpp
+++ b/filter_moog_f32.cpp
@@ -27,18 +27,26 @@
 #include "filter_moog_f32.h"
 
 
+__inline__ float tanh_fast(float x)
+{
+  // rational tanh aproximation
+  float x2 = x * x;
+  float a = x * (135135.0f + x2 * (17325.0f + x2 * (378.0f + x2)));
+  float b = 135135.0f + x2 * (62370.0f + x2 * (3150.0f + x2 * 28.0f));
+  return a / b;
+}
 
 #if defined(KINETISK)
 
 void AudioFilterMoog_F32::update_fixed(const float *in,float *lp)
 {
 	for (int i = 0; i < 2*AUDIO_BLOCK_SAMPLES; i++) {
-		float cs = tanhf(in[i/2] * driv);
-		y_a = y_a + g * (tanhf(cs - q * ((y_d_1 + y_d)/2) - tanhf(y_a)));
-		y_b = y_b + g * (tanhf(y_a) - tanhf(y_b));
-		y_c = y_c + g * (tanhf(y_b) - tanhf(y_c));
+		float cs = tanh_fast(in[i/2] * driv);
+		y_a = y_a + g * (tanh_fast(cs - q * ((y_d_1 + y_d)/2) - tanh_fast(y_a)));
+		y_b = y_b + g * (tanh_fast(y_a) - tanh_fast(y_b));
+		y_c = y_c + g * (tanh_fast(y_b) - tanh_fast(y_c));
 		y_d_1 = y_d;
-		y_d = y_d + g * (tanhf(y_c) - tanhf(y_d));
+		y_d = y_d + g * (tanh_fast(y_c) - tanh_fast(y_d));
 		lp[i/2]  = y_d;
 	}
 }
@@ -50,12 +58,12 @@ void AudioFilterMoog_F32::update_variable(const float *in,const float *ctl, floa
 		float nf=basef*(exp2f(ctl[0/over]*oct));
 		frequency(nf,false);
 	for (int i = 0; i < 2*AUDIO_BLOCK_SAMPLES; i++) {
-		float cs = tanhf(in[i/over] * driv);
-		y_a = y_a + g * (tanhf(cs - q * ((y_d_1 + y_d)/2) - tanhf(y_a)));
-		y_b = y_b + g * (tanhf(y_a) - tanhf(y_b));
-		y_c = y_c + g * (tanhf(y_b) - tanhf(y_c));
+		float cs = tanh_fast(in[i/over] * driv);
+		y_a = y_a + g * (tanh_fast(cs - q * ((y_d_1 + y_d)/2) - tanh_fast(y_a)));
+		y_b = y_b + g * (tanh_fast(y_a) - tanh_fast(y_b));
+		y_c = y_c + g * (tanh_fast(y_b) - tanh_fast(y_c));
 		y_d_1 = y_d;
-		y_d = y_d + g * (tanhf(y_c) - tanhf(y_d));
+		y_d = y_d + g * (tanh_fast(y_c) - tanh_fast(y_d));
 		lp[i/over]  = y_d;
 	}
 }
diff --git a/filter_moog_f32.h b/filter_moog_f32.h
index 072f6fa..9e6c179 100644
--- a/filter_moog_f32.h
+++ b/filter_moog_f32.h
@@ -28,7 +28,7 @@
 #define filter_moog_f32_h_
 
 #include "Arduino.h"
-#include "AudioStream_f32.h"
+#include "AudioStream_F32.h"
 #include "utility/dspinst.h"
 #include "arm_math.h"
 
@@ -52,7 +52,7 @@ public:
 	frequency(1000);
 	resonance(1);
 	drive(1);
-	octave(1);
+	octaveControl(1);
 	y_a = 0;
 	y_b = 0;
 	y_c = 0;
@@ -60,19 +60,19 @@ public:
 	y_d_1 = 0;
 	}
 	void frequency(float freq,bool setf=true) {
+		if(setf)
+			basef=freq;
 		if (freq < 20.0) freq = 20.0;
 		else if (freq > AUDIO_SAMPLE_RATE_EXACT/2.5) freq = AUDIO_SAMPLE_RATE_EXACT/2.5;
 	    g = 1 - expf(-2 * tanf(2 * M_PI * freq/(2 * AUDIO_SAMPLE_RATE_EXACT)));
 //		Serial.println(freq);
-		if(setf)
-			basef=freq;
 	}
 	void resonance(float qi) {
 		if (qi < 0.7) qi = 0.7;
 		else if (qi > 5.0) qi = 5.0;
 		q=qi;
 	}
-	void octave(float n) {
+	void octaveControl(float n) {
 		if (n < 0.0) n = 0.0;
 		else if (n > 6.9999) n = 6.9999;
 		oct=n;