diff --git a/engine.c b/engine.c
index b6288d9..9bc9125 100644
--- a/engine.c
+++ b/engine.c
@@ -11,29 +11,25 @@
 #include "engine.h"
 #include "psyn.h"
 
-static double _freqs[128];
-
-struct engine_t _engine;
-
-void engine_init()
+void engine_init(struct engine_t *engine)
 {
 	uint32_t i;
 
 	for (i = 0; i < 128; i++) {
-		_freqs[i] = 440.0 * pow(2.0, (i - 69.0) / 12.0);
+		engine->freqs[i] = 440.0 * pow(2.0, (i - 69.0) / 12.0);
 	}
 
 	osc_init();
-	engine_load_program();
+	engine_load_program(engine);
 }
 
-void engine_load_program()
+void engine_load_program(struct engine_t *engine)
 {
 	FILE *f = fopen("program.txt", "r");
 
 	while (!feof(f)) {
 		char buf[1024];
-		size_t l = fgets(buf, sizeof buf, f);
+		fgets(buf, sizeof buf, f);
 
 		if (!strncmp(buf, "voice", 5)) {
 			// Ignore voice
@@ -42,8 +38,8 @@ void engine_load_program()
 			float freq;
 			int r = sscanf(buf, "lfo %d %f", &lfo, &freq);
 			if (r >= 2 && lfo >= 0 && lfo < NUM_LFO) {
-				osc_setfreq(&_engine.lfo[lfo], freq);
-				_engine.lfo[lfo].level = 1.0;
+				osc_setfreq(&engine->lfo[lfo], freq);
+				engine->lfo[lfo].level = 1.0;
 			}
 		} else if (!strncmp(buf, "osc", 3)) {
 			int osc;
@@ -61,10 +57,10 @@ void engine_load_program()
 				else if (!strcmp(sshape, "MOOGSAW")) shape = OSC_MOOGSAW;
 				else if (!strcmp(sshape, "EXP")) shape = OSC_EXP;
 
-				_engine.params[osc].shape.value = shape;
-				_engine.params[osc].level.value = level;
-				_engine.params[osc].freq_mult.value = freq;
-				_engine.params[osc].phase.value = phase;
+				engine->params[osc].shape.value = shape;
+				engine->params[osc].level.value = level;
+				engine->params[osc].freq_mult.value = freq;
+				engine->params[osc].phase.value = phase;
 			}
 		} else if (!strncmp(buf, "pan", 3)) {
 			int pan;
@@ -75,17 +71,17 @@ void engine_load_program()
 			if (r >= 4 && pan >= 0 && pan <= VOICE_OSCILLATORS) {
 				int source = 0;
 				if (!strcmp(ssource, "FIXED")) {
-					_engine.params[pan].pan_type = PAN_FIXED;
-					_engine.params[pan].pan_level = parm1;
-					_engine.params[pan].pan_level_r = parm2;
+					engine->params[pan].pan_type = PAN_FIXED;
+					engine->params[pan].pan_level = parm1;
+					engine->params[pan].pan_level_r = parm2;
 				} else if (!strcmp(ssource, "OSC")) {
-					_engine.params[pan].pan_type = PAN_OSC;
-					_engine.params[pan].pan_source = parm1;
-					_engine.params[pan].pan_level = parm2;
+					engine->params[pan].pan_type = PAN_OSC;
+					engine->params[pan].pan_source = parm1;
+					engine->params[pan].pan_level = parm2;
 				} else if (!strcmp(ssource, "LFO")) {
-					_engine.params[pan].pan_type = PAN_LFO;
-					_engine.params[pan].pan_source = parm1;
-					_engine.params[pan].pan_level = parm2;
+					engine->params[pan].pan_type = PAN_LFO;
+					engine->params[pan].pan_source = parm1;
+					engine->params[pan].pan_level = parm2;
 				}
 			}
 		} else if (!strncmp(buf, "env", 3)) {
@@ -97,7 +93,7 @@ void engine_load_program()
 			float release;
 			int r = sscanf(buf, "env %d %f %f %f %f %f", &env, &attack, &hold, &decay, &sustain, &release);
 			if (r >= 6 && env >= 0 && env < VOICE_OSCILLATORS) {
-				env_init(&_engine.params[env].env, attack, hold, decay, sustain, release);
+				env_init(&engine->params[env].env, attack, hold, decay, sustain, release);
 			}
 		} else if (!strncmp(buf, "cutoff_env", 10)) {
 			int env;
@@ -108,7 +104,7 @@ void engine_load_program()
 			float release;
 			int r = sscanf(buf, "cutoff_env %d %f %f %f %f %f", &env, &attack, &hold, &decay, &sustain, &release);
 			if (r >= 6 && env >= 0 && env < 1) {
-				env_init(&_engine.cutoff_env, attack, hold, decay, sustain, release);
+				env_init(&engine->cutoff_env, attack, hold, decay, sustain, release);
 			}
 		}
 	}
@@ -122,20 +118,20 @@ void engine_run(struct engine_t *engine, uint32_t samples, float *left, float *r
 	uint32_t i;
 
 	for (pos = 0; pos < samples; pos++) {
-		control_tick(&_engine.lowpass);
+		control_tick(&engine->lowpass);
 
 		left[pos] = 0.0;
 		right[pos] = 0.0;
 
 		for (i = 0; i < NUM_LFO; i++) {
-			osc_tick(&_engine.lfo[i]);
+			osc_tick(&engine->lfo[i]);
 		}
 
-		v = _engine.voice;
+		v = engine->voice;
 		for (i = 0; i < NUM_POLYPHONY; i++, v++) {
 			if (!v->playing) continue;
 
-			voice_run(v, 1, left + pos, right + pos);
+			voice_run(v, engine, 1, left + pos, right + pos);
 		}
 	}
 }
@@ -154,7 +150,7 @@ void engine_startvoice(struct engine_t *engine, uint8_t note, uint8_t velocity)
 		v->velocity = velocity / 127.0;
 
 		/* Voice parameters which determine sound */
-		voice_init(v, _freqs[note]);
+		voice_init(v, engine, engine->freqs[note]);
 		return;
 	}
 
@@ -169,7 +165,7 @@ void engine_startvoice(struct engine_t *engine, uint8_t note, uint8_t velocity)
 		v->velocity = velocity / 127.0;
 
 		/* Voice parameters which determine sound */
-		voice_init(v, _freqs[note]);
+		voice_init(v, engine, engine->freqs[note]);
 
 		return;
 	}
diff --git a/engine.h b/engine.h
index 94c78f9..db4e410 100644
--- a/engine.h
+++ b/engine.h
@@ -16,12 +16,12 @@ struct engine_t
 	struct envelope_t cutoff_env;
 
 	struct voice_t voice[NUM_POLYPHONY];
+
+	double freqs[128];
 };
 
-extern struct engine_t _engine;
-
-void engine_init();
-void engine_load_program();
+void engine_init(struct engine_t *engine);
+void engine_load_program(struct engine_t *engine);
 void engine_run(struct engine_t *engine, uint32_t samples, float *left, float *right);
 void engine_startvoice(struct engine_t *engine, uint8_t note, uint8_t velocity);
 void engine_endvoice(struct engine_t *engine, uint8_t note, uint8_t velocity);
diff --git a/env.c b/env.c
index d60f6d7..18187a3 100644
--- a/env.c
+++ b/env.c
@@ -17,7 +17,7 @@ void env_init(struct envelope_t *env, double attack, double attack_hold, double
 	env->release_s     = env->release * _sample_rate;
 }
 
-double env_getamplitude(struct envelope_t *env, uint32_t sample, uint32_t released)
+double env_getamplitude(const struct envelope_t *env, uint32_t sample, uint32_t released)
 {
 	double amplitude;
 
diff --git a/env.h b/env.h
index 8a7c77f..69030ca 100644
--- a/env.h
+++ b/env.h
@@ -16,5 +16,5 @@ struct envelope_t
 };
 
 void env_init(struct envelope_t *env, double attack, double attack_hold, double decay, double sustain, double release);
-double env_getamplitude(struct envelope_t *env, uint32_t sample, uint32_t released);
+double env_getamplitude(const struct envelope_t *env, uint32_t sample, uint32_t released);
 
diff --git a/osc.h b/osc.h
index 1d44c5c..fa9fd47 100644
--- a/osc.h
+++ b/osc.h
@@ -42,13 +42,13 @@ static inline void osc_tick(struct osc_t *osc)
 	//osc->tri = _tri_table[pos];
 }
 
-static inline double osc_getsample(struct osc_t *osc)
+static inline double osc_getsample(const struct osc_t *osc)
 {
 	uint32_t pos = osc->ramp;
 	return _lookup_table[osc->shape][pos] * osc->level;
 }
 
-static inline double osc_getsamplewithphase(struct osc_t *osc, float phase)
+static inline double osc_getsamplewithphase(const struct osc_t *osc, float phase)
 {
 	double sample = osc->ramp + phase * LOOKUP_SAMPLES;
 	if (sample < 0.0) sample += LOOKUP_SAMPLES;
diff --git a/psyn.c b/psyn.c
index 96cdcdb..af140fe 100644
--- a/psyn.c
+++ b/psyn.c
@@ -26,13 +26,15 @@ struct psyn_t
 	float *ctrlLP;
 	float *ctrlOscShape[4];
 	float *ctrlOscLevel[4];
+
+	struct engine_t engine;
 };
 
 static void psyn_init(struct psyn_t *psyn, uint32_t sample_rate)
 {
 	_sample_rate = sample_rate;
 
-	engine_init();
+	engine_init(&psyn->engine);
 }
 
 static LV2_Handle instantiate(
@@ -107,6 +109,7 @@ static void run(LV2_Handle lv2instance, uint32_t sample_count)
 {
 	uint8_t i;
 	struct psyn_t *psyn = (struct psyn_t *)lv2instance;
+	struct engine_t *engine = &psyn->engine;
 	uint32_t frame = 0;
 	LV2_Event *ev = NULL;
 	LV2_Event_Iterator iterator;
@@ -115,8 +118,8 @@ static void run(LV2_Handle lv2instance, uint32_t sample_count)
 
 	if (lv2_event_is_valid(&iterator)) ev = lv2_event_get(&iterator, NULL);
 
-	control_setstep(&_engine.lowpass, *psyn->ctrlLP, sample_count);
-	_engine.monosynth = (int)*psyn->ctrlMono;
+	control_setstep(&engine->lowpass, *psyn->ctrlLP, sample_count);
+	engine->monosynth = (int)*psyn->ctrlMono;
 //	for (i = 0; i < 4; i++) {
 //		_engine.params[i].shape.value = *psyn->ctrlOscShape[i];
 //		_engine.params[i].level.value = *psyn->ctrlOscLevel[i];
@@ -131,7 +134,7 @@ static void run(LV2_Handle lv2instance, uint32_t sample_count)
 			to = sample_count;
 		}
 
-		engine_run(&_engine, to - frame, psyn->out_l + frame, psyn->out_r + frame);
+		engine_run(engine, to - frame, psyn->out_l + frame, psyn->out_r + frame);
 		frame = to;
 
 		if (ev != NULL) {
@@ -142,31 +145,31 @@ static void run(LV2_Handle lv2instance, uint32_t sample_count)
 
 				switch (data[0] & 0xF0) {
 					case 0x80:
-						engine_endvoice(&_engine, data[1], data[2]);
+						engine_endvoice(engine, data[1], data[2]);
 						break;
 
 					case 0x90:
-						engine_startvoice(&_engine, data[1], data[2]);
+						engine_startvoice(engine, data[1], data[2]);
 						break;
 
 					case 0xA0:
-						engine_aftertouch(&_engine, data[2]);
+						engine_aftertouch(engine, data[2]);
 						break;
 
 					case 0xC0:
-						engine_programchange(&_engine, data[1]);
+						engine_programchange(engine, data[1]);
 						break;
 
 					case 0xB0:
-						engine_controlchange(&_engine, data[1], data[2]);
+						engine_controlchange(engine, data[1], data[2]);
 						break;
 
 					case 0xD0:
-						engine_aftertouch(&_engine, data[1]);
+						engine_aftertouch(engine, data[1]);
 						break;
 
 					case 0xE0:
-						engine_pitchchange(&_engine, (data[1] | data[2] << 7) - 0x2000);
+						engine_pitchchange(engine, (data[1] | data[2] << 7) - 0x2000);
 						break;
 				}
 			}
diff --git a/voice.c b/voice.c
index 179f333..5c8f0e4 100644
--- a/voice.c
+++ b/voice.c
@@ -16,7 +16,7 @@ static inline double max(double a, double b)
 	return a > b ? a : b;
 }
 
-void voice_init(struct voice_t *voice, double freq)
+void voice_init(struct voice_t *voice, const struct engine_t *engine, double freq)
 {
 	uint8_t i;
 //	filter_init_rc(&voice->fil[0], 1000.0, 0.000000047);
@@ -27,11 +27,11 @@ void voice_init(struct voice_t *voice, double freq)
 //	bw_filter_init_lp(&voice->bw[0], _engine.lowpass.value, 1.0);
 
 	for (i = 0; i < VOICE_OSCILLATORS; i++) {
-		voice->osc[i].shape = _engine.params[i].shape.value;
-		voice->osc[i].level = _engine.params[i].level.value;
+		voice->osc[i].shape = engine->params[i].shape.value;
+		voice->osc[i].level = engine->params[i].level.value;
 
-		osc_setfreq(&voice->osc[i], freq * _engine.params[i].freq_mult.value);
-		osc_setphase(&voice->osc[i], _engine.params[i].phase.value);
+		osc_setfreq(&voice->osc[i], freq * engine->params[i].freq_mult.value);
+		osc_setphase(&voice->osc[i], engine->params[i].phase.value);
 	}
 }
 
@@ -45,7 +45,7 @@ static inline void voice_tick(struct voice_t *voice)
 	voice->sample++;
 }
 
-void voice_run(struct voice_t *voice, uint32_t samples, float *left, float *right)
+void voice_run(struct voice_t *voice, const struct engine_t *engine, uint32_t samples, float *left, float *right)
 {
 //	uint32_t pos;
 	int i;
@@ -58,7 +58,7 @@ void voice_run(struct voice_t *voice, uint32_t samples, float *left, float *righ
 
 	double amplitude = 0.0;
 	for (i = 0; i < VOICE_OSCILLATORS; i++) {
-		a[i] = env_getamplitude(&_engine.params[i].env, voice->sample, voice->released);
+		a[i] = env_getamplitude(&engine->params[i].env, voice->sample, voice->released);
 		amplitude += a[i];
 		a[i] *= voice->velocity;
 	}
@@ -69,23 +69,24 @@ void voice_run(struct voice_t *voice, uint32_t samples, float *left, float *righ
 	}
 
 	for (i = 0; i < VOICE_OSCILLATORS; i++) {
+		const struct voice_param_t *params = &engine->params[i];
 		float ss;
 		float pl = osc_getsample(&voice->osc[i]);
 		float pr = pl;
 		// Mix
 
-		switch (_engine.params[i].pan_type) {
+		switch (params->pan_type) {
 			case PAN_FIXED:
-				pl *= _engine.params[i].pan_level;
-				pr *= _engine.params[i].pan_level_r;
+				pl *= params->pan_level;
+				pr *= params->pan_level_r;
 				break;
 			case PAN_OSC:
-				ss = osc_getsample(&voice->osc[_engine.params[i].pan_source]) * _engine.params[i].pan_level * 0.5;
+				ss = osc_getsample(&voice->osc[params->pan_source]) * params->pan_level * 0.5;
 				pl *= 0.5 + ss;
 				pr *= 0.5 - ss;
 				break;
 			case PAN_LFO:
-				ss = osc_getsample(&_engine.lfo[_engine.params[i].pan_source]) * _engine.params[i].pan_level * 0.5;
+				ss = osc_getsample(&engine->lfo[params->pan_source]) * params->pan_level * 0.5;
 				pl *= 0.5 + ss;
 				pr *= 0.5 - ss;
 				break;
@@ -119,8 +120,8 @@ void voice_run(struct voice_t *voice, uint32_t samples, float *left, float *righ
 
 	double out_l, out_r;
 
-	double cutoff = max(env_getamplitude(&_engine.cutoff_env, voice->sample, 0), _engine.aftertouch.value) * 8000.0;
-	bw_filter_init_lp(&voice->bw[0], _engine.lowpass.value + cutoff, 1.0);
+	double cutoff = max(env_getamplitude(&engine->cutoff_env, voice->sample, 0), engine->aftertouch.value) * 8000.0;
+	bw_filter_init_lp(&voice->bw[0], engine->lowpass.value + cutoff, 1.0);
 	bw_filter_run(&voice->bw[0], l, r, &out_l, &out_r);
 //	filter_run_lp(&voice->fil[0], l, r);
 //	filter_run_hp(&voice->fil[1], voice->fil[0].last_out_l, voice->fil[0].last_out_r);
diff --git a/voice.h b/voice.h
index 44eff7a..8c0e8d3 100644
--- a/voice.h
+++ b/voice.h
@@ -38,5 +38,7 @@ struct voice_t
 	struct bw_filter_t bw[VOICE_FILTERS];
 };
 
-void voice_init(struct voice_t *voice, double freq);
-void voice_run(struct voice_t *voice, uint32_t samples, float *left, float *right);
+struct engine_t;
+
+void voice_init(struct voice_t *voice, const struct engine_t *engine, double freq);
+void voice_run(struct voice_t *voice, const struct engine_t *engine, uint32_t samples, float *left, float *right);