diff --git a/src/libespeak-ng/klatt.c b/src/libespeak-ng/klatt.c
index 15341912..8ce8fc0b 100644
--- a/src/libespeak-ng/klatt.c
+++ b/src/libespeak-ng/klatt.c
@@ -40,9 +40,7 @@
 #include "klatt.h"
 
 extern unsigned char *out_ptr;
-extern unsigned char *out_start;
 extern unsigned char *out_end;
-extern WGEN_DATA wdata;
 static int nsamples;
 static int sample_count;
 
@@ -63,6 +61,7 @@ static double gen_noise(double);
 static double DBtoLIN(long);
 static void frame_init(klatt_frame_ptr);
 static void setabc(long, long, resonator_ptr);
+static void SetSynth_Klatt(int length, frame_t *fr1, frame_t *fr2, voice_t *v, int control);
 static void setzeroabc(long, long, resonator_ptr);
 
 static klatt_frame_t kt_frame;
@@ -242,7 +241,7 @@ static double sampled_source(int source_num)
    Converts synthesis parameters to a waveform.
  */
 
-static int parwave(klatt_frame_ptr frame)
+static int parwave(klatt_frame_ptr frame, WGEN_DATA *wdata)
 {
 	double temp;
 	int value;
@@ -376,24 +375,24 @@ static int parwave(klatt_frame_ptr frame)
 		out = outbypas - out;
 
 		out = resonator(&(kt_globals.rsn[Rout]), out);
-		temp = (int)(out * wdata.amplitude * kt_globals.amp_gain0); // Convert back to integer
+		temp = (int)(out * wdata->amplitude * kt_globals.amp_gain0); // Convert back to integer
 
 		// mix with a recorded WAV if required for this phoneme
 		signed char c;
 		int sample;
 
-		if (wdata.mix_wavefile_ix < wdata.n_mix_wavefile) {
-			if (wdata.mix_wave_scale == 0) {
+		if (wdata->mix_wavefile_ix < wdata->n_mix_wavefile) {
+			if (wdata->mix_wave_scale == 0) {
 				// a 16 bit sample
-				c = wdata.mix_wavefile[wdata.mix_wavefile_ix+1];
-				sample = wdata.mix_wavefile[wdata.mix_wavefile_ix] + (c * 256);
-				wdata.mix_wavefile_ix += 2;
+				c = wdata->mix_wavefile[wdata->mix_wavefile_ix+1];
+				sample = wdata->mix_wavefile[wdata->mix_wavefile_ix] + (c * 256);
+				wdata->mix_wavefile_ix += 2;
 			} else {
 				// a 8 bit sample, scaled
-				sample = (signed char)wdata.mix_wavefile[wdata.mix_wavefile_ix++] * wdata.mix_wave_scale;
+				sample = (signed char)wdata->mix_wavefile[wdata->mix_wavefile_ix++] * wdata->mix_wave_scale;
 			}
-			int z2 = sample * wdata.amplitude_v / 1024;
-			z2 = (z2 * wdata.mix_wave_amp)/40;
+			int z2 = sample * wdata->amplitude_v / 1024;
+			z2 = (z2 * wdata->mix_wave_amp)/40;
 			temp += z2;
 		}
 
@@ -838,15 +837,17 @@ static double DBtoLIN(long dB)
 	return (double)(amptable[dB]) * 0.001;
 }
 
-extern voice_t *wvoice;
 static klatt_peaks_t peaks[N_PEAKS];
 static int end_wave;
 static int klattp[N_KLATTP];
 static double klattp1[N_KLATTP];
 static double klattp_inc[N_KLATTP];
 
-static int Wavegen_Klatt(int resume)
+int Wavegen_Klatt(int length, int resume, frame_t *fr1, frame_t *fr2, WGEN_DATA *wdata, voice_t *wvoice)
 {
+	if (resume == 0)
+		SetSynth_Klatt(length, fr1, fr2, wvoice, 1);
+
 	int pk;
 	int x;
 	int ix;
@@ -856,7 +857,7 @@ static int Wavegen_Klatt(int resume)
 		sample_count = 0;
 
 	while (sample_count < nsamples) {
-		kt_frame.F0hz10 = (wdata.pitch * 10) / 4096;
+		kt_frame.F0hz10 = (wdata->pitch * 10) / 4096;
 
 		// formants F6,F7,F8 are fixed values for cascade resonators, set in KlattInit()
 		// but F6 is used for parallel resonator
@@ -904,10 +905,10 @@ static int Wavegen_Klatt(int resume)
 		}
 
 		// advance the pitch
-		wdata.pitch_ix += wdata.pitch_inc;
-		if ((ix = wdata.pitch_ix>>8) > 127) ix = 127;
-		x = wdata.pitch_env[ix] * wdata.pitch_range;
-		wdata.pitch = (x>>8) + wdata.pitch_base;
+		wdata->pitch_ix += wdata->pitch_inc;
+		if ((ix = wdata->pitch_ix>>8) > 127) ix = 127;
+		x = wdata->pitch_env[ix] * wdata->pitch_range;
+		wdata->pitch = (x>>8) + wdata->pitch_base;
 
 		kt_globals.nspfr = (nsamples - sample_count);
 		if (kt_globals.nspfr > STEPSIZE)
@@ -915,7 +916,7 @@ static int Wavegen_Klatt(int resume)
 
 		frame_init(&kt_frame); // get parameters for next frame of speech
 
-		if (parwave(&kt_frame) == 1)
+		if (parwave(&kt_frame, wdata) == 1)
 			return 1; // output buffer is full
 	}
 
@@ -927,14 +928,14 @@ static int Wavegen_Klatt(int resume)
 		end_wave = 0;
 		sample_count -= fade;
 		kt_globals.nspfr = fade;
-		if (parwave(&kt_frame) == 1)
+		if (parwave(&kt_frame, wdata) == 1)
 			return 1; // output buffer is full
 	}
 
 	return 0;
 }
 
-static void SetSynth_Klatt(int length, frame_t *fr1, frame_t *fr2, voice_t *v, int control)
+static void SetSynth_Klatt(int length, frame_t *fr1, frame_t *fr2, voice_t *wvoice, int control)
 {
 	int ix;
 	double next;
@@ -1004,9 +1005,9 @@ static void SetSynth_Klatt(int length, frame_t *fr1, frame_t *fr2, voice_t *v, i
 	nsamples = length;
 
 	for (ix = 1; ix < 6; ix++) {
-		peaks[ix].freq1 = (fr1->ffreq[ix] * v->freq[ix] / 256.0) + v->freqadd[ix];
+		peaks[ix].freq1 = (fr1->ffreq[ix] * wvoice->freq[ix] / 256.0) + wvoice->freqadd[ix];
 		peaks[ix].freq = (int)peaks[ix].freq1;
-		next = (fr2->ffreq[ix] * v->freq[ix] / 256.0) + v->freqadd[ix];
+		next = (fr2->ffreq[ix] * wvoice->freq[ix] / 256.0) + wvoice->freqadd[ix];
 		peaks[ix].freq_inc =  ((next - peaks[ix].freq1) * STEPSIZE) / length;
 
 		if (ix < 4) {
@@ -1050,14 +1051,6 @@ static void SetSynth_Klatt(int length, frame_t *fr1, frame_t *fr2, voice_t *v, i
 	}
 }
 
-int Wavegen_Klatt2(int length, int resume, frame_t *fr1, frame_t *fr2)
-{
-	if (resume == 0)
-		SetSynth_Klatt(length, fr1, fr2, wvoice, 1);
-
-	return Wavegen_Klatt(resume);
-}
-
 void KlattInit()
 {
 
diff --git a/src/libespeak-ng/klatt.h b/src/libespeak-ng/klatt.h
index f8acdb84..4c7a4406 100644
--- a/src/libespeak-ng/klatt.h
+++ b/src/libespeak-ng/klatt.h
@@ -179,8 +179,7 @@ typedef struct {
 
 void KlattInit(void);
 void KlattReset(int control);
-int Wavegen_Klatt2(int length, int resume, frame_t *fr1, frame_t *fr2);
-
+int Wavegen_Klatt(int length, int resume, frame_t *fr1, frame_t *fr2, WGEN_DATA *wdata, voice_t *wvoice);
 
 #ifdef __cplusplus
 }
diff --git a/src/libespeak-ng/phoneme.h b/src/libespeak-ng/phoneme.h
index e6ed1fc6..e46a3927 100644
--- a/src/libespeak-ng/phoneme.h
+++ b/src/libespeak-ng/phoneme.h
@@ -249,9 +249,7 @@ phoneme_add_feature(PHONEME_TAB *phoneme,
 // Several phoneme tables may be loaded into memory. phoneme_tab points to
 // one for the current voice
 extern int n_phoneme_tab;
-extern int current_phoneme_table;
 extern PHONEME_TAB *phoneme_tab[N_PHONEME_TAB];
-extern unsigned char phoneme_tab_flags[N_PHONEME_TAB];  // bit 0: not inherited
 
 typedef struct {
 	char name[N_PHONEME_TAB_NAME];
diff --git a/src/libespeak-ng/speech.c b/src/libespeak-ng/speech.c
index a9e0f336..331948ca 100644
--- a/src/libespeak-ng/speech.c
+++ b/src/libespeak-ng/speech.c
@@ -65,6 +65,7 @@
 
 unsigned char *outbuf = NULL;
 int outbuf_size = 0;
+unsigned char *out_start;
 
 espeak_EVENT *event_list = NULL;
 int event_list_ix = 0;
diff --git a/src/libespeak-ng/synthdata.c b/src/libespeak-ng/synthdata.c
index 7cee6996..8756847d 100644
--- a/src/libespeak-ng/synthdata.c
+++ b/src/libespeak-ng/synthdata.c
@@ -45,9 +45,7 @@ const int version_phdata  = 0x014801;
 
 // copy the current phoneme table into here
 int n_phoneme_tab;
-int current_phoneme_table;
 PHONEME_TAB *phoneme_tab[N_PHONEME_TAB];
-unsigned char phoneme_tab_flags[N_PHONEME_TAB];   // bit 0: not inherited
 
 unsigned short *phoneme_index = NULL;
 char *phondata_ptr = NULL;
@@ -62,7 +60,6 @@ int wavefile_ix; // a wavefile to play along with the synthesis
 int wavefile_amp;
 
 int seq_len_adjust;
-int vowel_transition[4];
 
 static espeak_ng_STATUS ReadPhFile(void **ptr, const char *fname, int *size, espeak_ng_ERROR_CONTEXT *context)
 {
@@ -331,19 +328,16 @@ unsigned char *GetEnvelope(int index)
 	return (unsigned char *)&phondata_ptr[index];
 }
 
-static void SetUpPhonemeTable(int number, bool recursing)
+static void SetUpPhonemeTable(int number)
 {
 	int ix;
 	int includes;
 	int ph_code;
 	PHONEME_TAB *phtab;
 
-	if (recursing == false)
-		memset(phoneme_tab_flags, 0, sizeof(phoneme_tab_flags));
-
 	if ((includes = phoneme_tab_list[number].includes) > 0) {
 		// recursively include base phoneme tables
-		SetUpPhonemeTable(includes-1, true);
+		SetUpPhonemeTable(includes - 1);
 	}
 
 	// now add the phonemes from this table
@@ -353,18 +347,15 @@ static void SetUpPhonemeTable(int number, bool recursing)
 		phoneme_tab[ph_code] = &phtab[ix];
 		if (ph_code > n_phoneme_tab)
 			n_phoneme_tab = ph_code;
-
-		if (recursing == 0)
-			phoneme_tab_flags[ph_code] |= 1; // not inherited
 	}
 }
 
-void SelectPhonemeTable(int number)
+int SelectPhonemeTable(int number)
 {
 	n_phoneme_tab = 0;
-	SetUpPhonemeTable(number, false); // recursively for included phoneme tables
+	SetUpPhonemeTable(number); // recursively for included phoneme tables
 	n_phoneme_tab++;
-	current_phoneme_table = number;
+	return number;
 }
 
 int LookupPhonemeTable(const char *name)
diff --git a/src/libespeak-ng/synthdata.h b/src/libespeak-ng/synthdata.h
index a199c96f..aac12e51 100644
--- a/src/libespeak-ng/synthdata.h
+++ b/src/libespeak-ng/synthdata.h
@@ -52,7 +52,7 @@ frameref_t *LookupSpect(PHONEME_TAB *this_ph,
 
 int NumInstnWords(unsigned short *prog);
 int PhonemeCode(unsigned int mnem);
-void SelectPhonemeTable(int number);
+int SelectPhonemeTable(int number);
 int  SelectPhonemeTableName(const char *name);
 
 #ifdef __cplusplus
diff --git a/src/libespeak-ng/synthesize.c b/src/libespeak-ng/synthesize.c
index 70cd8243..ddf78757 100644
--- a/src/libespeak-ng/synthesize.c
+++ b/src/libespeak-ng/synthesize.c
@@ -44,7 +44,6 @@
 #include "synthesize.h"
 #include "translate.h"
 
-extern FILE *f_log;
 static void SmoothSpect(void);
 
 // list of phonemes in a clause
@@ -127,7 +126,6 @@ static void EndPitch(int voice_break)
 		syllable_end = wcmdq_tail;
 		SmoothSpect();
 		syllable_centre = -1;
-		memset(vowel_transition, 0, sizeof(vowel_transition));
 	}
 }
 
@@ -1190,7 +1188,6 @@ int Generate(PHONEME_LIST *phoneme_list, int *n_ph, bool resume)
 		syllable_end = wcmdq_tail;
 		syllable_centre = -1;
 		last_pitch_cmd = -1;
-		memset(vowel_transition, 0, sizeof(vowel_transition));
 		memset(&worddata, 0, sizeof(worddata));
 		DoPause(0, 0); // isolate from the previous clause
 	}
@@ -1549,6 +1546,7 @@ int Generate(PHONEME_LIST *phoneme_list, int *n_ph, bool resume)
 	return 0; // finished the phoneme list
 }
 
+static int current_phoneme_table;
 int SpeakNextClause(int control)
 {
 	// Speak text from memory (text_in)
@@ -1577,7 +1575,7 @@ int SpeakNextClause(int control)
 	}
 
 	if (current_phoneme_table != voice->phoneme_tab_ix)
-		SelectPhonemeTable(voice->phoneme_tab_ix);
+		current_phoneme_table = SelectPhonemeTable(voice->phoneme_tab_ix);
 
 	// read the next clause from the input text file, translate it, and generate
 	// entries in the wavegen command queue
diff --git a/src/libespeak-ng/synthesize.h b/src/libespeak-ng/synthesize.h
index 90cd7533..ba4e76d3 100644
--- a/src/libespeak-ng/synthesize.h
+++ b/src/libespeak-ng/synthesize.h
@@ -450,7 +450,6 @@ extern int samplerate_native;
 
 extern int wavefile_ix;
 extern int wavefile_amp;
-extern int vowel_transition[4];
 
 #define N_ECHO_BUF 5500   // max of 250mS at 22050 Hz
 extern int echo_head;
@@ -482,7 +481,6 @@ extern int formant_rate[];         // max rate of change of each formant
 extern SPEED_FACTORS speed;
 
 extern unsigned char *out_ptr;
-extern unsigned char *out_start;
 extern unsigned char *out_end;
 extern espeak_EVENT *event_list;
 extern t_espeak_callback *synth_callback;
diff --git a/src/libespeak-ng/wavegen.c b/src/libespeak-ng/wavegen.c
index e48868cb..b161b46f 100644
--- a/src/libespeak-ng/wavegen.c
+++ b/src/libespeak-ng/wavegen.c
@@ -51,9 +51,10 @@
 
 #define N_WAV_BUF   10
 
+static void SetSynth(int length, int modn, frame_t *fr1, frame_t *fr2, voice_t *v);
+
 voice_t *wvoice = NULL;
 
-FILE *f_log = NULL;
 static int option_harmonic1 = 10;
 static int flutter_amp = 64;
 
@@ -113,7 +114,6 @@ static double minus_pi_t;
 static double two_pi_t;
 
 unsigned char *out_ptr;
-unsigned char *out_start;
 unsigned char *out_end;
 
 espeak_ng_OUTPUT_HOOKS* output_hooks = NULL;
@@ -680,8 +680,11 @@ static int ApplyBreath(void)
 	return value;
 }
 
-static int Wavegen()
+static int Wavegen(int length, int modulation, bool resume, frame_t *fr1, frame_t *fr2, voice_t *wvoice)
 {
+	if (resume == false)
+		SetSynth(length, modulation, fr1, fr2, wvoice);
+
 	if (wvoice == NULL)
 		return 0;
 
@@ -1245,14 +1248,6 @@ static void SetSynth(int length, int modn, frame_t *fr1, frame_t *fr2, voice_t *
 	}
 }
 
-static int Wavegen2(int length, int modulation, bool resume, frame_t *fr1, frame_t *fr2)
-{
-	if (resume == false)
-		SetSynth(length, modulation, fr1, fr2, wvoice);
-
-	return Wavegen();
-}
-
 void Write4Bytes(FILE *f, int value)
 {
 	// Write 4 bytes to a file, least significant first
@@ -1339,14 +1334,14 @@ static int WavegenFill2()
 			wdata.n_mix_wavefile = 0; // ... and drop through to WCMD_SPECT case
 		case WCMD_SPECT:
 			echo_complete = echo_length;
-			result = Wavegen2(length & 0xffff, q[1] >> 16, resume, (frame_t *)q[2], (frame_t *)q[3]);
+			result = Wavegen(length & 0xffff, q[1] >> 16, resume, (frame_t *)q[2], (frame_t *)q[3], wvoice);
 			break;
 #ifdef INCLUDE_KLATT
 		case WCMD_KLATT2: // as WCMD_SPECT but stop any concurrent wave file
 			wdata.n_mix_wavefile = 0; // ... and drop through to WCMD_SPECT case
 		case WCMD_KLATT:
 			echo_complete = echo_length;
-			result = Wavegen_Klatt2(length & 0xffff, resume, (frame_t *)q[2], (frame_t *)q[3]);
+			result = Wavegen_Klatt(length & 0xffff, resume, (frame_t *)q[2], (frame_t *)q[3], &wdata, wvoice);
 			break;
 #endif
 		case WCMD_MARKER: