diff -Naur festival.orig/src/modules/clustergen/HTS_vocoder_me.cc festival/src/modules/clustergen/HTS_vocoder_me.cc
--- festival.orig/src/modules/clustergen/HTS_vocoder_me.cc	2013-02-18 16:10:50.000000000 +0100
+++ festival/src/modules/clustergen/HTS_vocoder_me.cc	2015-07-28 18:25:52.846670680 +0200
@@ -90,8 +90,9 @@
 
 HTS_VOCODER_ME_C_START;
 
+#include <math.h>
 #include "./HTS_vocoder_me.h"
-#include "../hts_engine/HTS_vocoder.c"
+#include "../hts_engine/HTS_vocoder.h"
 
 /* HTS_Vocoder_initialize_me: initialize vocoder (mixed excitation) */
 void HTS_Vocoder_initialize_me(HTS_Vocoder_ME * v_me,
diff -Naur festival.orig/src/modules/hts_engine/HTS_vocoder.c festival/src/modules/hts_engine/HTS_vocoder.c
--- festival.orig/src/modules/hts_engine/HTS_vocoder.c	2013-02-18 16:10:52.000000000 +0100
+++ festival/src/modules/hts_engine/HTS_vocoder.c	2015-07-28 18:26:22.680173336 +0200
@@ -57,10 +57,12 @@
 
 #include <math.h>               /* for sqrt(),log(),exp(),pow(),cos() */
 
+//#include "HTS_vocoder.h"
+
 /* hts_engine libraries */
 #include "HTS_hidden.h"
 
-static const double HTS_pade[21] = {
+const double HTS_pade[21] = {
    1.00000000000,
    1.00000000000,
    0.00000000000,
@@ -85,7 +87,7 @@
 };
 
 /* HTS_movem: move memory */
-static void HTS_movem(double *a, double *b, const int nitem)
+void HTS_movem(double *a, double *b, const int nitem)
 {
    long i = (long) nitem;
 
@@ -101,7 +103,7 @@
 }
 
 /* HTS_mlsafir: sub functions for MLSA filter */
-static double HTS_mlsafir(const double x, const double *b, const int m, const double a, const double aa, double *d)
+double HTS_mlsafir(const double x, const double *b, const int m, const double a, const double aa, double *d)
 {
    double y = 0.0;
    int i;
@@ -122,7 +124,7 @@
 }
 
 /* HTS_mlsadf1: sub functions for MLSA filter */
-static double HTS_mlsadf1(double x, const double *b, const int m, const double a, const double aa, const int pd, double *d, const double *ppade)
+double HTS_mlsadf1(double x, const double *b, const int m, const double a, const double aa, const int pd, double *d, const double *ppade)
 {
    double v, out = 0.0, *pt;
    int i;
@@ -144,7 +146,7 @@
 }
 
 /* HTS_mlsadf2: sub functions for MLSA filter */
-static double HTS_mlsadf2(double x, const double *b, const int m, const double a, const double aa, const int pd, double *d, const double *ppade)
+double HTS_mlsadf2(double x, const double *b, const int m, const double a, const double aa, const int pd, double *d, const double *ppade)
 {
    double v, out = 0.0, *pt;
    int i;
@@ -166,7 +168,7 @@
 }
 
 /* HTS_mlsadf: functions for MLSA filter */
-static double HTS_mlsadf(double x, const double *b, const int m, const double a, const int pd, double *d)
+double HTS_mlsadf(double x, const double *b, const int m, const double a, const int pd, double *d)
 {
    const double aa = 1 - a * a;
    const double *ppade = &(HTS_pade[pd * (pd + 1) / 2]);
@@ -178,7 +180,7 @@
 }
 
 /* HTS_rnd: functions for random noise generation */
-static double HTS_rnd(unsigned long *next)
+double HTS_rnd(unsigned long *next)
 {
    double r;
 
@@ -189,7 +191,7 @@
 }
 
 /* HTS_nrandom: functions for gaussian random noise generation */
-static double HTS_nrandom(HTS_Vocoder * v)
+double HTS_nrandom(HTS_Vocoder * v)
 {
    if (v->sw == 0) {
       v->sw = 1;
@@ -207,7 +209,7 @@
 }
 
 /* HTS_mceq: function for M-sequence random noise generation */
-static int HTS_mseq(HTS_Vocoder * v)
+int HTS_mseq(HTS_Vocoder * v)
 {
    int x0, x28;
 
@@ -229,7 +231,7 @@
 }
 
 /* HTS_mc2b: transform mel-cepstrum to MLSA digital fillter coefficients */
-static void HTS_mc2b(double *mc, double *b, int m, const double a)
+void HTS_mc2b(double *mc, double *b, int m, const double a)
 {
    if (mc != b) {
       if (a != 0.0) {
@@ -244,7 +246,7 @@
 }
 
 /* HTS_b2bc: transform MLSA digital filter coefficients to mel-cepstrum */
-static void HTS_b2mc(const double *b, double *mc, int m, const double a)
+void HTS_b2mc(const double *b, double *mc, int m, const double a)
 {
    double d, o;
 
@@ -257,7 +259,7 @@
 }
 
 /* HTS_freqt: frequency transformation */
-static void HTS_freqt(HTS_Vocoder * v, const double *c1, const int m1, double *c2, const int m2, const double a)
+void HTS_freqt(HTS_Vocoder * v, const double *c1, const int m1, double *c2, const int m2, const double a)
 {
    int i, j;
    const double b = 1 - a * a;
@@ -287,7 +289,7 @@
 }
 
 /* HTS_c2ir: The minimum phase impulse response is evaluated from the minimum phase cepstrum */
-static void HTS_c2ir(const double *c, const int nc, double *h, const int leng)
+void HTS_c2ir(const double *c, const int nc, double *h, const int leng)
 {
    int n, k, upl;
    double d;
@@ -303,7 +305,7 @@
 }
 
 /* HTS_b2en: calculate frame energy */
-static double HTS_b2en(HTS_Vocoder * v, const double *b, const int m, const double a)
+double HTS_b2en(HTS_Vocoder * v, const double *b, const int m, const double a)
 {
    int i;
    double en = 0.0;
@@ -330,7 +332,7 @@
 }
 
 /* HTS_ignorm: inverse gain normalization */
-static void HTS_ignorm(double *c1, double *c2, int m, const double g)
+void HTS_ignorm(double *c1, double *c2, int m, const double g)
 {
    double k;
    if (g != 0.0) {
@@ -345,7 +347,7 @@
 }
 
 /* HTS_gnorm: gain normalization */
-static void HTS_gnorm(double *c1, double *c2, int m, const double g)
+void HTS_gnorm(double *c1, double *c2, int m, const double g)
 {
    double k;
    if (g != 0.0) {
@@ -360,7 +362,7 @@
 }
 
 /* HTS_lsp2lpc: transform LSP to LPC */
-static void HTS_lsp2lpc(HTS_Vocoder * v, double *lsp, double *a, const int m)
+void HTS_lsp2lpc(HTS_Vocoder * v, double *lsp, double *a, const int m)
 {
    int i, k, mh1, mh2, flag_odd;
    double xx, xf, xff;
@@ -451,7 +453,7 @@
 }
 
 /* HTS_gc2gc: generalized cepstral transformation */
-static void HTS_gc2gc(HTS_Vocoder * v, double *c1, const int m1, const double g1, double *c2, const int m2, const double g2)
+void HTS_gc2gc(HTS_Vocoder * v, double *c1, const int m1, const double g1, double *c2, const int m2, const double g2)
 {
    int i, min, k, mk;
    double ss1, ss2, cc;
@@ -484,7 +486,7 @@
 }
 
 /* HTS_mgc2mgc: frequency and generalized cepstral transformation */
-static void HTS_mgc2mgc(HTS_Vocoder * v, double *c1, const int m1, const double a1, const double g1, double *c2, const int m2, const double a2, const double g2)
+void HTS_mgc2mgc(HTS_Vocoder * v, double *c1, const int m1, const double a1, const double g1, double *c2, const int m2, const double a2, const double g2)
 {
    double a;
 
@@ -502,7 +504,7 @@
 }
 
 /* HTS_lsp2mgc: transform LSP to MGC */
-static void HTS_lsp2mgc(HTS_Vocoder * v, double *lsp, double *mgc, const int m, const double alpha)
+void HTS_lsp2mgc(HTS_Vocoder * v, double *lsp, double *mgc, const int m, const double alpha)
 {
    int i;
    /* lsp2lpc */
@@ -531,7 +533,7 @@
 }
 
 /* HTS_mglsadff: sub functions for MGLSA filter */
-static double HTS_mglsadff(double x, const double *b, const int m, const double a, double *d)
+double HTS_mglsadff(double x, const double *b, const int m, const double a, double *d)
 {
    int i;
 
@@ -550,7 +552,7 @@
 }
 
 /* HTS_mglsadf: sub functions for MGLSA filter */
-static double HTS_mglsadf(double x, const double *b, const int m, const double a, const int n, double *d)
+double HTS_mglsadf(double x, const double *b, const int m, const double a, const int n, double *d)
 {
    int i;
 
@@ -561,7 +563,7 @@
 }
 
 /* THS_check_lsp_stability: check LSP stability */
-static void HTS_check_lsp_stability(double *lsp, size_t m)
+void HTS_check_lsp_stability(double *lsp, size_t m)
 {
    size_t i, j;
    double tmp;
@@ -595,7 +597,7 @@
 }
 
 /* HTS_lsp2en: calculate frame energy */
-static double HTS_lsp2en(HTS_Vocoder * v, double *lsp, size_t m, double alpha)
+double HTS_lsp2en(HTS_Vocoder * v, double *lsp, size_t m, double alpha)
 {
    size_t i;
    double en = 0.0;
@@ -632,7 +634,7 @@
 }
 
 /* HTS_white_noise: return white noise */
-static double HTS_white_noise(HTS_Vocoder * v)
+double HTS_white_noise(HTS_Vocoder * v)
 {
    if (v->gauss)
       return (double) HTS_nrandom(v);
@@ -641,7 +643,7 @@
 }
 
 /* HTS_ping_pulse: ping pulse using low-pass filter */
-static void HTS_ping_pulse(HTS_Vocoder * v, const int ping_place, const double p, const int nlpf, const double *lpf)
+void HTS_ping_pulse(HTS_Vocoder * v, const int ping_place, const double p, const int nlpf, const double *lpf)
 {
    int i, j;
    const double power = sqrt(p);
@@ -652,7 +654,7 @@
 }
 
 /* HTS_ping_noise: ping noise using low-pass filter */
-static void HTS_ping_noise(HTS_Vocoder * v, const int ping_place, const int nlpf, const double *lpf)
+void HTS_ping_noise(HTS_Vocoder * v, const int ping_place, const int nlpf, const double *lpf)
 {
    int i, j;
    const double power = HTS_white_noise(v);
@@ -667,7 +669,7 @@
 }
 
 /* HTS_Vocoder_initialize_excitation: initialize excitation */
-static void HTS_Vocoder_initialize_excitation(HTS_Vocoder * v, size_t nlpf)
+void HTS_Vocoder_initialize_excitation(HTS_Vocoder * v, size_t nlpf)
 {
    size_t i;
 
@@ -684,7 +686,7 @@
 }
 
 /* HTS_Vocoder_start_excitation: start excitation of each frame */
-static void HTS_Vocoder_start_excitation(HTS_Vocoder * v, const double pitch, const int nlpf)
+void HTS_Vocoder_start_excitation(HTS_Vocoder * v, const double pitch, const int nlpf)
 {
    if (v->p1 != 0.0 && pitch != 0.0)
       v->inc = (pitch - v->p1) * IPERIOD / v->fprd;
@@ -699,7 +701,7 @@
 }
 
 /* HTS_Vocoder_get_excitation: get excitation of each sample */
-static double HTS_Vocoder_get_excitation(HTS_Vocoder * v, const int fprd_index, const int iprd_index, const int nlpf, const double *lpf)
+double HTS_Vocoder_get_excitation(HTS_Vocoder * v, const int fprd_index, const int iprd_index, const int nlpf, const double *lpf)
 {
    double x;
    int i, j;
@@ -755,7 +757,7 @@
 }
 
 /* HTS_Vocoder_end_excitation: end excitation of each frame */
-static void HTS_Vocoder_end_excitation(HTS_Vocoder * v, const int nlpf)
+void HTS_Vocoder_end_excitation(HTS_Vocoder * v, const int nlpf)
 {
    int i;
 
@@ -771,7 +773,7 @@
 }
 
 /* HTS_Vocoder_postfilter_mcp: postfilter for MCP */
-static void HTS_Vocoder_postfilter_mcp(HTS_Vocoder * v, double *mcp, const int m, double alpha, double beta)
+void HTS_Vocoder_postfilter_mcp(HTS_Vocoder * v, double *mcp, const int m, double alpha, double beta)
 {
    double e1, e2;
    int k;
@@ -797,7 +799,7 @@
 }
 
 /* HTS_Vocoder_postfilter_lsp: postfilter for LSP */
-static void HTS_Vocoder_postfilter_lsp(HTS_Vocoder * v, double *lsp, size_t m, double alpha, double beta)
+void HTS_Vocoder_postfilter_lsp(HTS_Vocoder * v, double *lsp, size_t m, double alpha, double beta)
 {
    double e1, e2;
    size_t i;
diff -Naur festival.orig/src/modules/hts_engine/HTS_vocoder.h festival/src/modules/hts_engine/HTS_vocoder.h
--- festival.orig/src/modules/hts_engine/HTS_vocoder.h	1970-01-01 01:00:00.000000000 +0100
+++ festival/src/modules/hts_engine/HTS_vocoder.h	2015-07-28 18:21:15.431802892 +0200
@@ -0,0 +1,42 @@
+#ifndef HTS_VOCODER_H
+#define HTS_VOCODER_H
+
+/* hts_engine libraries */
+#include "HTS_hidden.h"
+
+void HTS_Vocoder_clear(HTS_Vocoder *v);
+void HTS_Vocoder_synthesize(HTS_Vocoder *v,size_t m,double lf0,double *spectrum,size_t nlpf,double *lpf,double alpha,double beta,double volume,double *rawdata,HTS_Audio *audio);
+void HTS_Vocoder_initialize(HTS_Vocoder *v,size_t m,size_t stage,HTS_Boolean use_log_gain,size_t rate,size_t fperiod);
+void HTS_Vocoder_postfilter_lsp(HTS_Vocoder *v,double *lsp,size_t m,double alpha,double beta);
+void HTS_Vocoder_postfilter_mcp(HTS_Vocoder *v,double *mcp,const int m,double alpha,double beta);
+void HTS_Vocoder_end_excitation(HTS_Vocoder *v,const int nlpf);
+double HTS_Vocoder_get_excitation(HTS_Vocoder *v,const int fprd_index,const int iprd_index,const int nlpf,const double *lpf);
+void HTS_Vocoder_start_excitation(HTS_Vocoder *v,const double pitch,const int nlpf);
+void HTS_Vocoder_initialize_excitation(HTS_Vocoder *v,size_t nlpf);
+void HTS_ping_noise(HTS_Vocoder *v,const int ping_place,const int nlpf,const double *lpf);
+void HTS_ping_pulse(HTS_Vocoder *v,const int ping_place,const double p,const int nlpf,const double *lpf);
+double HTS_white_noise(HTS_Vocoder *v);
+double HTS_lsp2en(HTS_Vocoder *v,double *lsp,size_t m,double alpha);
+void HTS_check_lsp_stability(double *lsp,size_t m);
+double HTS_mglsadf(double x,const double *b,const int m,const double a,const int n,double *d);
+double HTS_mglsadff(double x,const double *b,const int m,const double a,double *d);
+void HTS_lsp2mgc(HTS_Vocoder *v,double *lsp,double *mgc,const int m,const double alpha);
+void HTS_mgc2mgc(HTS_Vocoder *v,double *c1,const int m1,const double a1,const double g1,double *c2,const int m2,const double a2,const double g2);
+void HTS_gc2gc(HTS_Vocoder *v,double *c1,const int m1,const double g1,double *c2,const int m2,const double g2);
+void HTS_lsp2lpc(HTS_Vocoder *v,double *lsp,double *a,const int m);
+void HTS_gnorm(double *c1,double *c2,int m,const double g);
+void HTS_ignorm(double *c1,double *c2,int m,const double g);
+double HTS_b2en(HTS_Vocoder *v,const double *b,const int m,const double a);
+void HTS_c2ir(const double *c,const int nc,double *h,const int leng);
+void HTS_freqt(HTS_Vocoder *v,const double *c1,const int m1,double *c2,const int m2,const double a);
+void HTS_b2mc(const double *b,double *mc,int m,const double a);
+void HTS_mc2b(double *mc,double *b,int m,const double a);
+int HTS_mseq(HTS_Vocoder *v);
+double HTS_nrandom(HTS_Vocoder *v);
+double HTS_rnd(unsigned long *next);
+double HTS_mlsadf(double x,const double *b,const int m,const double a,const int pd,double *d);
+double HTS_mlsadf2(double x,const double *b,const int m,const double a,const double aa,const int pd,double *d,const double *ppade);
+double HTS_mlsadf1(double x,const double *b,const int m,const double a,const double aa,const int pd,double *d,const double *ppade);
+double HTS_mlsafir(const double x,const double *b,const int m,const double a,const double aa,double *d);
+void HTS_movem(double *a,double *b,const int nitem);
+#endif