diff --git a/mt32emu_qt/src/QSynth.cpp b/mt32emu_qt/src/QSynth.cpp
index c3f5185..14a0cce 100644
--- a/mt32emu_qt/src/QSynth.cpp
+++ b/mt32emu_qt/src/QSynth.cpp
@@ -22,6 +22,7 @@
 #include "AudioFileWriter.h"
 #include "Master.h"
 #include "MasterClock.h"
+#include "RealtimeLocker.h"
 
 using namespace MT32Emu;
 
@@ -72,25 +73,6 @@ static int readMasterVolume(Synth *synth) {
 	return masterVolume;
 }
 
-class RealtimeLocker {
-private:
-	QMutex &mutex;
-	bool locked;
-
-public:
-	explicit RealtimeLocker(QMutex &useMutex) : mutex(useMutex) {
-		locked = mutex.tryLock();
-	}
-
-	~RealtimeLocker() {
-		if (locked) mutex.unlock();
-	}
-
-	bool isLocked() {
-		return locked;
-	}
-};
-
 class RealtimeHelper : public QThread {
 private:
 	enum SynthControlEvent {
diff --git a/mt32emu_qt/src/RealtimeLocker.h b/mt32emu_qt/src/RealtimeLocker.h
new file mode 100644
index 0000000..87de37d
--- /dev/null
+++ b/mt32emu_qt/src/RealtimeLocker.h
@@ -0,0 +1,43 @@
+/* Copyright (C) 2011-2020 Jerome Fisher, Sergey V. Mikayev
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef REALTIME_LOCKER_H
+#define REALTIME_LOCKER_H
+
+#include "QMutex"
+
+// Similar to QMutexLocker but intended to be used from a realtime thread that should never block.
+class RealtimeLocker {
+private:
+	QMutex &mutex;
+	bool locked;
+
+public:
+	explicit RealtimeLocker(QMutex &useMutex) : mutex(useMutex) {
+		locked = mutex.tryLock();
+	}
+
+	~RealtimeLocker() {
+		if (locked) mutex.unlock();
+		locked = false;
+	}
+
+	bool isLocked() {
+		return locked;
+	}
+};
+
+#endif // REALTIME_LOCKER_H