diff --git a/plugins/sfxr/sfxr.cpp b/plugins/sfxr/sfxr.cpp
index ab1132197..66f9b58a1 100644
--- a/plugins/sfxr/sfxr.cpp
+++ b/plugins/sfxr/sfxr.cpp
@@ -23,7 +23,8 @@
  * Boston, MA 02110-1301 USA.
  */
 
-#include <stdlib.h>
+#include <cstdlib>
+#include <time.h>
 
 #define rnd(n) (rand()%(n+1))
 
@@ -447,7 +448,6 @@ QString sfxrInstrument::nodeName() const
 
 void sfxrInstrument::playNote( notePlayHandle * _n, sampleFrame * _working_buffer )
 {
-	m_synthMutex.lock();
     fpp_t frameNum = _n->framesLeftForCurrentPeriod();
 	if ( _n->totalFramesPlayed() == 0 )
 	{
@@ -456,6 +456,7 @@ void sfxrInstrument::playNote( notePlayHandle * _n, sampleFrame * _working_buffe
 	else if( static_cast<SfxrSynth*>(_n->m_pluginData)->isPlaying() == false )
 	{
 		_n->noteOff();
+		return;
 	}
 
 	fpp_t pitchedFrameNum = (_n->frequency()/BaseFreq)*frameNum;
@@ -470,7 +471,6 @@ void sfxrInstrument::playNote( notePlayHandle * _n, sampleFrame * _working_buffe
 	}
 
 	delete[] pitchedBuffer;
-	m_synthMutex.unlock();
 
 	instrumentTrack()->processAudioBuffer( _working_buffer, frameNum, NULL );
 }
diff --git a/plugins/sfxr/sfxr.h b/plugins/sfxr/sfxr.h
index 2d9934219..20250db70 100644
--- a/plugins/sfxr/sfxr.h
+++ b/plugins/sfxr/sfxr.h
@@ -184,7 +184,6 @@ public:
 
 
 private:
-	QMutex m_synthMutex;
 	SfxrZeroToOneFloatModel m_attModel;
 	SfxrZeroToOneFloatModel m_holdModel;
 	SfxrZeroToOneFloatModel m_susModel;