diff --git a/src/audio/AudioStream.cpp b/src/audio/AudioStream.cpp
index 0ceece5..25667b5 100644
--- a/src/audio/AudioStream.cpp
+++ b/src/audio/AudioStream.cpp
@@ -1,9 +1,9 @@
 #include "AudioStream.h"
 
-TimeRange AudioStream::getTruncatedRange() {
+TimeRange AudioStream::getTruncatedRange() const {
 	return TimeRange(centiseconds::zero(), centiseconds(100 * getSampleCount() / getSampleRate()));
 }
 
-bool AudioStream::endOfStream() {
+bool AudioStream::endOfStream() const {
 	return getSampleIndex() >= getSampleCount();
 }
diff --git a/src/audio/AudioStream.h b/src/audio/AudioStream.h
index 41df2ff..f368be3 100644
--- a/src/audio/AudioStream.h
+++ b/src/audio/AudioStream.h
@@ -7,12 +7,12 @@
 class AudioStream {
 public:
 	virtual ~AudioStream() {}
-	virtual std::unique_ptr<AudioStream> clone(bool reset) = 0;
-	virtual int getSampleRate() = 0;
-	virtual int getSampleCount() = 0;
-	TimeRange getTruncatedRange();
-	virtual int getSampleIndex() = 0;
+	virtual std::unique_ptr<AudioStream> clone(bool reset) const = 0;
+	virtual int getSampleRate() const = 0;
+	virtual int getSampleCount() const = 0;
+	TimeRange getTruncatedRange() const;
+	virtual int getSampleIndex() const = 0;
 	virtual void seek(int sampleIndex) = 0;
-	bool endOfStream();
+	bool endOfStream() const;
 	virtual float readSample() = 0;
 };
diff --git a/src/audio/DCOffset.cpp b/src/audio/DCOffset.cpp
index 1316e3b..dcde649 100644
--- a/src/audio/DCOffset.cpp
+++ b/src/audio/DCOffset.cpp
@@ -14,19 +14,19 @@ DCOffset::DCOffset(const DCOffset& rhs, bool reset) :
 	factor(rhs.factor)
 {}
 
-std::unique_ptr<AudioStream> DCOffset::clone(bool reset) {
+std::unique_ptr<AudioStream> DCOffset::clone(bool reset) const {
 	return std::make_unique<DCOffset>(*this, reset);
 }
 
-int DCOffset::getSampleRate() {
+int DCOffset::getSampleRate() const {
 	return inputStream->getSampleRate();
 }
 
-int DCOffset::getSampleCount() {
+int DCOffset::getSampleCount() const {
 	return inputStream->getSampleCount();
 }
 
-int DCOffset::getSampleIndex() {
+int DCOffset::getSampleIndex() const {
 	return inputStream->getSampleIndex();
 }
 
diff --git a/src/audio/DCOffset.h b/src/audio/DCOffset.h
index 070fd3d..b5d6cb5 100644
--- a/src/audio/DCOffset.h
+++ b/src/audio/DCOffset.h
@@ -8,10 +8,10 @@ class DCOffset : public AudioStream {
 public:
 	DCOffset(std::unique_ptr<AudioStream> inputStream, float offset);
 	DCOffset(const DCOffset& rhs, bool reset);
-	std::unique_ptr<AudioStream> clone(bool reset) override;
-	int getSampleRate() override;
-	int getSampleCount() override;
-	int getSampleIndex() override;
+	std::unique_ptr<AudioStream> clone(bool reset) const override;
+	int getSampleRate() const override;
+	int getSampleCount() const override;
+	int getSampleIndex() const override;
 	void seek(int sampleIndex) override;
 	float readSample() override;
 
diff --git a/src/audio/SampleRateConverter.cpp b/src/audio/SampleRateConverter.cpp
index d94a8f0..0f4b1a0 100644
--- a/src/audio/SampleRateConverter.cpp
+++ b/src/audio/SampleRateConverter.cpp
@@ -29,19 +29,19 @@ SampleRateConverter::SampleRateConverter(const SampleRateConverter& rhs, bool re
 	nextOutputSampleIndex = reset ? 0 : rhs.nextOutputSampleIndex;
 }
 
-std::unique_ptr<AudioStream> SampleRateConverter::clone(bool reset) {
+std::unique_ptr<AudioStream> SampleRateConverter::clone(bool reset) const {
 	return std::make_unique<SampleRateConverter>(*this, reset);
 }
 
-int SampleRateConverter::getSampleRate() {
+int SampleRateConverter::getSampleRate() const {
 	return outputSampleRate;
 }
 
-int SampleRateConverter::getSampleCount() {
+int SampleRateConverter::getSampleCount() const {
 	return outputSampleCount;
 }
 
-int SampleRateConverter::getSampleIndex() {
+int SampleRateConverter::getSampleIndex() const {
 	return nextOutputSampleIndex;
 }
 
diff --git a/src/audio/SampleRateConverter.h b/src/audio/SampleRateConverter.h
index 50835d4..14dfa21 100644
--- a/src/audio/SampleRateConverter.h
+++ b/src/audio/SampleRateConverter.h
@@ -7,10 +7,10 @@ class SampleRateConverter : public AudioStream {
 public:
 	SampleRateConverter(std::unique_ptr<AudioStream> inputStream, int outputSampleRate);
 	SampleRateConverter(const SampleRateConverter& rhs, bool reset);
-	std::unique_ptr<AudioStream> clone(bool reset) override;
-	int getSampleRate() override;
-	int getSampleCount() override;
-	int getSampleIndex() override;
+	std::unique_ptr<AudioStream> clone(bool reset) const override;
+	int getSampleRate() const override;
+	int getSampleCount() const override;
+	int getSampleIndex() const override;
 	void seek(int sampleIndex) override;
 	float readSample() override;
 private:
diff --git a/src/audio/UnboundedStream.cpp b/src/audio/UnboundedStream.cpp
index cd38ea8..ecd88fb 100644
--- a/src/audio/UnboundedStream.cpp
+++ b/src/audio/UnboundedStream.cpp
@@ -16,19 +16,19 @@ UnboundedStream::UnboundedStream(const UnboundedStream& rhs, bool reset) :
 	lastSample(rhs.lastSample)
 {}
 
-std::unique_ptr<AudioStream> UnboundedStream::clone(bool reset) {
+std::unique_ptr<AudioStream> UnboundedStream::clone(bool reset) const {
 	return std::make_unique<UnboundedStream>(*this, reset);
 }
 
-int UnboundedStream::getSampleRate() {
+int UnboundedStream::getSampleRate() const {
 	return innerStream->getSampleRate();
 }
 
-int UnboundedStream::getSampleCount() {
+int UnboundedStream::getSampleCount() const {
 	return innerStream->getSampleCount();
 }
 
-int UnboundedStream::getSampleIndex() {
+int UnboundedStream::getSampleIndex() const {
 	return sampleIndex;
 }
 
diff --git a/src/audio/UnboundedStream.h b/src/audio/UnboundedStream.h
index d20e441..09bc787 100644
--- a/src/audio/UnboundedStream.h
+++ b/src/audio/UnboundedStream.h
@@ -8,10 +8,10 @@ class UnboundedStream : public AudioStream {
 public:
 	UnboundedStream(std::unique_ptr<AudioStream> inputStream);
 	UnboundedStream(const UnboundedStream& rhs, bool reset);
-	std::unique_ptr<AudioStream> clone(bool reset) override;
-	int getSampleRate() override;
-	int getSampleCount() override;
-	int getSampleIndex() override;
+	std::unique_ptr<AudioStream> clone(bool reset) const override;
+	int getSampleRate() const override;
+	int getSampleCount() const override;
+	int getSampleIndex() const override;
 	void seek(int sampleIndex) override;
 	float readSample() override;
 
diff --git a/src/audio/WaveFileReader.cpp b/src/audio/WaveFileReader.cpp
index 269879e..f3b574a 100644
--- a/src/audio/WaveFileReader.cpp
+++ b/src/audio/WaveFileReader.cpp
@@ -148,7 +148,7 @@ WaveFileReader::WaveFileReader(const WaveFileReader& rhs, bool reset) :
 	seek(reset ? 0 : rhs.sampleIndex);
 }
 
-std::unique_ptr<AudioStream> WaveFileReader::clone(bool reset) {
+std::unique_ptr<AudioStream> WaveFileReader::clone(bool reset) const {
 	return std::make_unique<WaveFileReader>(*this, reset);
 }
 
@@ -170,15 +170,15 @@ void WaveFileReader::openFile() {
 	}
 }
 
-int WaveFileReader::getSampleRate() {
+int WaveFileReader::getSampleRate() const {
 	return frameRate;
 }
 
-int WaveFileReader::getSampleCount() {
+int WaveFileReader::getSampleCount() const {
 	return frameCount;
 }
 
-int WaveFileReader::getSampleIndex() {
+int WaveFileReader::getSampleIndex() const {
 	return sampleIndex;
 }
 
diff --git a/src/audio/WaveFileReader.h b/src/audio/WaveFileReader.h
index 3946a2a..4b34ec3 100644
--- a/src/audio/WaveFileReader.h
+++ b/src/audio/WaveFileReader.h
@@ -15,10 +15,10 @@ class WaveFileReader : public AudioStream {
 public:
 	WaveFileReader(boost::filesystem::path filePath);
 	WaveFileReader(const WaveFileReader& rhs, bool reset);
-	std::unique_ptr<AudioStream> clone(bool reset) override;
-	int getSampleRate() override ;
-	int getSampleCount() override;
-	int getSampleIndex() override;
+	std::unique_ptr<AudioStream> clone(bool reset) const override;
+	int getSampleRate() const override ;
+	int getSampleCount() const override;
+	int getSampleIndex() const override;
 	void seek(int sampleIndex) override;
 	float readSample() override;