diff --git a/.gitmodules b/.gitmodules
index 05fb6b53645..94530a19710 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -18,7 +18,7 @@
 	url = https://github.com/lmms/veal
 [submodule "plugins/Xpressive/exprtk"]
 	path = plugins/Xpressive/exprtk
-	url = https://github.com/tresf/exprtk
+	url = https://github.com/ArashPartow/exprtk
 [submodule "plugins/LadspaEffect/swh/ladspa"]
 	path = plugins/LadspaEffect/swh/ladspa
 	url = https://github.com/swh/ladspa
diff --git a/plugins/Xpressive/ExprSynth.cpp b/plugins/Xpressive/ExprSynth.cpp
index 90ac1474d07..4e5ba21e826 100644
--- a/plugins/Xpressive/ExprSynth.cpp
+++ b/plugins/Xpressive/ExprSynth.cpp
@@ -296,30 +296,58 @@ inline unsigned int rotateLeft(unsigned int x, const int b)
 	return x;
 }
 
-struct RandomVectorFunction : public exprtk::ifunction<float>
+struct RandomVectorSeedFunction : public exprtk::ifunction<float>
 {
 	using exprtk::ifunction<float>::operator();
 
-	RandomVectorFunction(const unsigned int seed) :
-	exprtk::ifunction<float>(1),
-	m_rseed(seed)
+	RandomVectorSeedFunction() :
+	exprtk::ifunction<float>(2)
 	{ exprtk::disable_has_side_effects(*this); }
 
-	inline float operator()(const float& index)
+	static inline float randv(const float& index,int irseed)
 	{
 		if (index < 0 || std::isnan(index) || std::isinf(index))
 		{
 			return 0;
 		}
 		const unsigned int xi = (unsigned int)index;
-		const unsigned int si = m_rseed % data_size;
-		const unsigned int sa = m_rseed / data_size;
-		unsigned int res=rotateLeft(random_data[(xi + si) % data_size] ^ random_data[(xi / data_size + sa) % data_size],sa % 31 + 1);
-		res ^= rotateLeft(random_data[(3 * xi + si) % data_size] ^ random_data[(xi / data_size + 2 * sa) % data_size],xi % 31 + 1);
+		const unsigned int si = irseed % data_size;
+		const unsigned int sa = irseed / data_size;
+		unsigned int res=rotateLeft(random_data[(xi + 23 * si + 1) % data_size] ^ random_data[(xi / data_size + sa) % data_size],sa % 31 + 1);
+		res ^= rotateLeft(random_data[(3 * xi + si + 13) % data_size],(xi+2*si) % 32) ^rotateLeft( random_data[(xi / data_size + 2 * sa) % data_size],xi % 31 + 1);
 		return static_cast<int>(res) / (float)(1 << 31);
 	}
 
-	const int data_size=sizeof(random_data)/sizeof(int);
+	inline float operator()(const float& index,const float& seed)
+	{
+		int irseed;
+		if (seed < 0 || std::isnan(seed) || std::isinf(seed))
+		{
+			irseed=0;
+		}
+		else
+			irseed=(int)seed;
+		return randv(index,irseed);
+	}
+
+	static const int data_size=sizeof(random_data)/sizeof(int);
+};
+static RandomVectorSeedFunction randsv_func;
+
+struct RandomVectorFunction : public exprtk::ifunction<float>
+{
+	using exprtk::ifunction<float>::operator();
+
+	RandomVectorFunction(const unsigned int seed) :
+	exprtk::ifunction<float>(1),
+	m_rseed(seed)
+	{ exprtk::disable_has_side_effects(*this); }
+
+	inline float operator()(const float& index)
+	{
+		return RandomVectorSeedFunction::randv(index,m_rseed);
+	}
+
 	const unsigned int m_rseed;
 };
 
@@ -340,10 +368,10 @@ static freefunc0<float,SimpleRandom::float_random_with_engine,false> simple_rand
 class ExprFrontData
 {
 public:
-	ExprFrontData():
+	ExprFrontData(int last_func_samples):
 	m_rand_vec(SimpleRandom::generator()),
 	m_integ_func(NULL),
-	m_last_func(500)
+	m_last_func(last_func_samples)
 	{}
 	~ExprFrontData()
 	{
@@ -369,6 +397,7 @@ class ExprFrontData
 	RandomVectorFunction m_rand_vec;
 	IntegrateFunction<float> *m_integ_func;
 	LastSampleFunction<float> m_last_func;
+
 };
 
 
@@ -489,17 +518,19 @@ struct harmonic_semitone
 static freefunc1<float,harmonic_semitone,true> harmonic_semitone_func;
 
 
-ExprFront::ExprFront(const char * expr)
+ExprFront::ExprFront(const char * expr, int last_func_samples)
 {
 	m_valid = false;
 	try
 	{
-		m_data = new ExprFrontData();
+		m_data = new ExprFrontData(last_func_samples);
 	
 		m_data->m_expression_string = expr;
 		m_data->m_symbol_table.add_pi();
 	
 		m_data->m_symbol_table.add_constant("e", F_E);
+
+		m_data->m_symbol_table.add_constant("seed", SimpleRandom::generator() & max_float_integer_mask);
 	
 		m_data->m_symbol_table.add_function("sinew", sin_wave_func);
 		m_data->m_symbol_table.add_function("squarew", square_wave_func);
@@ -513,6 +544,7 @@ ExprFront::ExprFront(const char * expr)
 		m_data->m_symbol_table.add_function("semitone", harmonic_semitone_func);
 		m_data->m_symbol_table.add_function("rand", simple_rand);
 		m_data->m_symbol_table.add_function("randv", m_data->m_rand_vec);
+		m_data->m_symbol_table.add_function("randsv", randsv_func);
 		m_data->m_symbol_table.add_function("last", m_data->m_last_func);
 	}
 	catch(...)
@@ -742,7 +774,7 @@ void ExprSynth::renderOutput(fpp_t frames, sampleFrame *buf)
 				}
 				o1 = o1_rawExpr->value();
 				o2 = o2_rawExpr->value();
-				last_func1->setLastSample(o1);
+				last_func1->setLastSample(o1);//put result in the circular buffer for the "last" function.
 				last_func2->setLastSample(o2);
 				buf[frame][0] = (-pn1 + 0.5) * o1 + (-pn2 + 0.5) * o2;
 				buf[frame][1] = ( pn1 + 0.5) * o1 + ( pn2 + 0.5) * o2;
diff --git a/plugins/Xpressive/ExprSynth.h b/plugins/Xpressive/ExprSynth.h
index a46aea8c650..bb25fd036dd 100644
--- a/plugins/Xpressive/ExprSynth.h
+++ b/plugins/Xpressive/ExprSynth.h
@@ -27,6 +27,7 @@
 
 #include <cmath>
 #include <cstddef>
+#include <limits>
 #include "AutomatableModel.h"
 #include "Graph.h"
 #include "Instrument.h"
@@ -39,7 +40,7 @@ class ExprFront
 {
 public:
 	typedef float (*ff1data_functor)(void*, float);
-	ExprFront(const char* expr);
+	ExprFront(const char* expr, int last_func_samples);
 	~ExprFront();
 	bool compile();
 	inline bool isValid() { return m_valid; }
@@ -52,6 +53,9 @@ class ExprFront
 private:
 	ExprFrontData *m_data;
 	bool m_valid;
+	
+	static const int max_float_integer_mask=(1<<(std::numeric_limits<float>::digits))-1;
+
 };
 
 class WaveSample
diff --git a/plugins/Xpressive/Xpressive.cpp b/plugins/Xpressive/Xpressive.cpp
index 5edd1e2044f..0dae72f6845 100644
--- a/plugins/Xpressive/Xpressive.cpp
+++ b/plugins/Xpressive/Xpressive.cpp
@@ -202,23 +202,24 @@ void Xpressive::playNote(NotePlayHandle* nph, sampleFrame* working_buffer) {
 
 	if (nph->totalFramesPlayed() == 0 || nph->m_pluginData == NULL) {
 
-		ExprFront *exprO1 = new ExprFront(m_outputExpression[0].constData());
-		ExprFront *exprO2 = new ExprFront(m_outputExpression[1].constData());
-
-		auto init_expression_step1 = [this, nph](ExprFront* e) {
-			e->add_constant("key", nph->key());
-			e->add_constant("bnote", nph->instrumentTrack()->baseNote());
-			e->add_constant("srate", Engine::mixer()->processingSampleRate());
-			e->add_constant("v", nph->getVolume() / 255.0);
-			e->add_constant("tempo", Engine::getSong()->getTempo());
-			e->add_variable("A1", m_A1);
+		ExprFront *exprO1 = new ExprFront(m_outputExpression[0].constData(),Engine::mixer()->processingSampleRate());//give the "last" function a whole second
+		ExprFront *exprO2 = new ExprFront(m_outputExpression[1].constData(),Engine::mixer()->processingSampleRate());
+
+		auto init_expression_step1 = [this, nph](ExprFront* e) { //lambda function to init exprO1 and exprO2
+			//add the constants and the variables to the expression.
+			e->add_constant("key", nph->key());//the key that was pressed.
+			e->add_constant("bnote", nph->instrumentTrack()->baseNote()); // the base note
+			e->add_constant("srate", Engine::mixer()->processingSampleRate());// sample rate of the mixer
+			e->add_constant("v", nph->getVolume() / 255.0); //volume of the note.
+			e->add_constant("tempo", Engine::getSong()->getTempo());//tempo of the song.
+			e->add_variable("A1", m_A1);//A1,A2,A3: general purpose input controls.
 			e->add_variable("A2", m_A2);
 			e->add_variable("A3", m_A3);
 		};
 		init_expression_step1(exprO1);
 		init_expression_step1(exprO2);
 
-		m_W1.setInterpolate(m_interpolateW1.value());
+		m_W1.setInterpolate(m_interpolateW1.value());//set interpolation according to the user selection.
 		m_W2.setInterpolate(m_interpolateW2.value());
 		m_W3.setInterpolate(m_interpolateW3.value());
 		nph->m_pluginData = new ExprSynth(&m_W1, &m_W2, &m_W3, exprO1, exprO2, nph,
@@ -520,11 +521,11 @@ void XpressiveView::expressionChanged() {
 
 	if (text.size()>0)
 	{
-		ExprFront expr(text.constData());
+		const unsigned int sample_rate=m_raw_graph->length();
+		ExprFront expr(text.constData(),sample_rate);
 		float t=0;
 		const float f=10,key=5,v=0.5;
 		unsigned int i;
-		const unsigned int sample_rate=m_raw_graph->length();
 		expr.add_variable("t", t);
 
 		if (m_output_expr)
@@ -776,7 +777,7 @@ void XpressiveView::sqrWaveClicked() {
 }
 
 void XpressiveView::noiseWaveClicked() {
-	m_expressionEditor->appendPlainText("rand");
+	m_expressionEditor->appendPlainText("randsv(t*srate,0)");
 	Engine::getSong()->setModified();
 }
 
@@ -821,13 +822,14 @@ QString XpressiveHelpView::s_helpText=
 "<b>rel</b> - Gives 0.0 while the key is holded, and 1.0 after the key release. Available only in the output expressions.<br>"
 "<b>trel</b> - Time after release. While the note is holded, it gives 0.0. Afterwards, it start counting seconds.<br>"
 "The time it takes to shift from 0.0 to 1.0 after key release is determined by the REL knob<br>"
+"<b>seed</b> - A random value that remains consistent in the lifetime of a single wave. meant to be used with <b>randsv</b><br>"
 "<b>A1, A2, A3</b> - General purpose knobs. You can reference them only in O1 and O2. In range [-1,1].<br>"
 "<h4>Available functions:</h4><br>"
 "<b>W1, W2, W3</b> - As mentioned before. You can reference them only in O1 and O2.<br>"
 "<b>cent(x)</b> - Gives pow(2,x/1200), so you can multiply it with the f variable to pitch the frequency.<br>"
 "100 cents equals one semitone<br>"
 "<b>semitone(x)</b> - Gives pow(2,x/12), so you can multiply it with the f variable to pitch the frequency.<br>"
-"<b>last(n)</b> - Gives you the last n'th evaluated sample. The argument n must be in the range [1,500], or else, it will return 0.<br>"
+"<b>last(n)</b> - Gives you the last n'th evaluated sample. In O1 and O2 it keeps a whole second. Thus the argument n must be in the range [1,srate], or else, it will return 0.<br>"
 "<b>integrate(x)</b> - Integrates x by delta t (It sums values and divides them by sample rate).<br>"
 "If you use notes with automated frequency, you should use:<br>"
 "sinew(integrate(f)) instead of sinew(t*f)<br>"
@@ -838,6 +840,9 @@ QString XpressiveHelpView::s_helpText=
 "and every reference to randv(a) will give you the same value."
 "If you want a random wave you can use randv(t*srate).<br>"
 "Each random value is in the range [-1,1).<br>"
+"<b>randsv(x,seed)</b> - works exactly like randv(x),<br>"
+"except that it lets you to select the seed manualy,<br>"
+"if you want to try different random values and make it consistent in each evaluation.<br>"
 "<b>sinew(x)</b> - A sine wave with period of 1 (In contrast to real sine wave which have a period of 2*pi).<br>"
 "<b>trianglew(x)</b> - A triangle wave with period of 1.<br>"
 "<b>squarew(x)</b> - A square wave with period of 1.<br>"
diff --git a/plugins/Xpressive/exprtk b/plugins/Xpressive/exprtk
index aad301a6ebb..f32d2b4bbb6 160000
--- a/plugins/Xpressive/exprtk
+++ b/plugins/Xpressive/exprtk
@@ -1 +1 @@
-Subproject commit aad301a6ebbab769620b0bb0e77713c4659117a6
+Subproject commit f32d2b4bbb640ea4732b8a7fce1bd9717e9c998b