diff --git a/libs/ardour/ardour/audio_playlist_source.h b/libs/ardour/ardour/audio_playlist_source.h
index e2eeb78a8d..7be61a30dc 100644
--- a/libs/ardour/ardour/audio_playlist_source.h
+++ b/libs/ardour/ardour/audio_playlist_source.h
@@ -40,7 +40,7 @@ public:
 	bool clamped_at_unity () const { return false; }
 
 	samplecnt_t read_unlocked (Sample *dst, samplepos_t start, samplecnt_t cnt) const;
-	samplecnt_t write_unlocked (Sample *src, samplecnt_t cnt);
+	samplecnt_t write_unlocked (Sample const * src, samplecnt_t cnt);
 
 	float sample_rate () const;
 	int setup_peakfile ();
diff --git a/libs/ardour/ardour/audiosource.h b/libs/ardour/ardour/audiosource.h
index 96f4938e3f..6a6b36db47 100644
--- a/libs/ardour/ardour/audiosource.h
+++ b/libs/ardour/ardour/audiosource.h
@@ -55,7 +55,7 @@ class LIBARDOUR_API AudioSource : virtual public Source, public ARDOUR::AudioRea
 	virtual samplecnt_t available_peaks (double zoom) const;
 
 	virtual samplecnt_t read (Sample *dst, samplepos_t start, samplecnt_t cnt, int channel=0) const;
-	virtual samplecnt_t write (Sample *src, samplecnt_t cnt);
+	virtual samplecnt_t write (Sample const * src, samplecnt_t cnt);
 
 	virtual float sample_rate () const = 0;
 
@@ -117,21 +117,21 @@ class LIBARDOUR_API AudioSource : virtual public Source, public ARDOUR::AudioRea
 
 	int initialize_peakfile (const std::string& path, const bool in_session = false);
 	int build_peaks_from_scratch ();
-	int compute_and_write_peaks (Sample* buf, samplecnt_t first_sample, samplecnt_t cnt,
+	int compute_and_write_peaks (Sample const * buf, samplecnt_t first_sample, samplecnt_t cnt,
 	bool force, bool intermediate_peaks_ready_signal);
 	void truncate_peakfile();
 
 	mutable off_t _peak_byte_max; // modified in compute_and_write_peak()
 
 	virtual samplecnt_t read_unlocked (Sample *dst, samplepos_t start, samplecnt_t cnt) const = 0;
-	virtual samplecnt_t write_unlocked (Sample *dst, samplecnt_t cnt) = 0;
+	virtual samplecnt_t write_unlocked (Sample const * dst, samplecnt_t cnt) = 0;
 	virtual std::string construct_peak_filepath (const std::string& audio_path, const bool in_session = false, const bool old_peak_name = false) const = 0;
 
 	virtual int read_peaks_with_fpp (PeakData *peaks,
 					 samplecnt_t npeaks, samplepos_t start, samplecnt_t cnt,
 					 double samples_per_visual_peak, samplecnt_t fpp) const;
 
-	int compute_and_write_peaks (Sample* buf, samplecnt_t first_sample, samplecnt_t cnt,
+	int compute_and_write_peaks (Sample const * buf, samplecnt_t first_sample, samplecnt_t cnt,
 				     bool force, bool intermediate_peaks_ready_signal,
 				     samplecnt_t samples_per_peak);
 
diff --git a/libs/ardour/ardour/coreaudiosource.h b/libs/ardour/ardour/coreaudiosource.h
index 2cc0dead0e..26130fd89a 100644
--- a/libs/ardour/ardour/coreaudiosource.h
+++ b/libs/ardour/ardour/coreaudiosource.h
@@ -55,7 +55,7 @@ class LIBARDOUR_API CoreAudioSource : public AudioFileSource {
   protected:
 	void close ();
 	samplecnt_t read_unlocked (Sample *dst, samplepos_t start, samplecnt_t cnt) const;
-	samplecnt_t write_unlocked (Sample *, samplecnt_t) { return 0; }
+	samplecnt_t write_unlocked (Sample const * src, samplecnt_t) { return 0; }
 
   private:
 #ifdef COREAUDIO105
diff --git a/libs/ardour/ardour/ffmpegfilesource.h b/libs/ardour/ardour/ffmpegfilesource.h
index 6ff891fc69..e4a90273f6 100644
--- a/libs/ardour/ardour/ffmpegfilesource.h
+++ b/libs/ardour/ardour/ffmpegfilesource.h
@@ -49,7 +49,7 @@ protected:
 	void close ();
 	/* AudioSource API */
 	samplecnt_t read_unlocked (Sample *dst, samplepos_t start, samplecnt_t cnt) const;
-	samplecnt_t write_unlocked (Sample *, samplecnt_t) { return 0; }
+	samplecnt_t write_unlocked (Sample const *, samplecnt_t) { return 0; }
 
 private:
 	mutable FFMPEGFileImportableSource _ffmpeg;
diff --git a/libs/ardour/ardour/mp3filesource.h b/libs/ardour/ardour/mp3filesource.h
index b423562cf7..3c829d5f5a 100644
--- a/libs/ardour/ardour/mp3filesource.h
+++ b/libs/ardour/ardour/mp3filesource.h
@@ -47,7 +47,7 @@ protected:
 	void close ();
 	/* AudioSource API */
 	samplecnt_t read_unlocked (Sample *dst, samplepos_t start, samplecnt_t cnt) const;
-	samplecnt_t write_unlocked (Sample *, samplecnt_t) { return 0; }
+	samplecnt_t write_unlocked (Sample const *, samplecnt_t) { return 0; }
 
 private:
 	mutable Mp3FileImportableSource _mp3;
diff --git a/libs/ardour/ardour/silentfilesource.h b/libs/ardour/ardour/silentfilesource.h
index 369fec496f..2bcbe68eca 100644
--- a/libs/ardour/ardour/silentfilesource.h
+++ b/libs/ardour/ardour/silentfilesource.h
@@ -58,7 +58,7 @@ protected:
 		return cnt;
 	}
 
-	samplecnt_t write_unlocked (Sample */*dst*/, samplecnt_t /*cnt*/) { return 0; }
+	samplecnt_t write_unlocked (Sample const * /*src*/, samplecnt_t /*cnt*/) { return 0; }
 
 	void set_header_natural_position () {}
 
diff --git a/libs/ardour/ardour/sndfilesource.h b/libs/ardour/ardour/sndfilesource.h
index 33d372d4f9..77a0e5503b 100644
--- a/libs/ardour/ardour/sndfilesource.h
+++ b/libs/ardour/ardour/sndfilesource.h
@@ -83,8 +83,8 @@ class LIBARDOUR_API SndFileSource : public AudioFileSource {
 	void set_header_natural_position ();
 
 	samplecnt_t read_unlocked (Sample *dst, samplepos_t start, samplecnt_t cnt) const;
-	samplecnt_t write_unlocked (Sample *dst, samplecnt_t cnt);
-	samplecnt_t write_float (Sample* data, samplepos_t pos, samplecnt_t cnt);
+	samplecnt_t write_unlocked (Sample const * dst, samplecnt_t cnt);
+	samplecnt_t write_float (Sample const * data, samplepos_t pos, samplecnt_t cnt);
 
   private:
 	SNDFILE* _sndfile;
@@ -97,7 +97,7 @@ class LIBARDOUR_API SndFileSource : public AudioFileSource {
 	void file_closed ();
 
 	void set_natural_position (timepos_t const &);
-	samplecnt_t nondestructive_write_unlocked (Sample *dst, samplecnt_t cnt);
+	samplecnt_t nondestructive_write_unlocked (Sample const *src, samplecnt_t cnt);
 	PBD::ScopedConnection header_position_connection;
 };
 
diff --git a/libs/ardour/ardour/srcfilesource.h b/libs/ardour/ardour/srcfilesource.h
index f027f4b327..a5629ba031 100644
--- a/libs/ardour/ardour/srcfilesource.h
+++ b/libs/ardour/ardour/srcfilesource.h
@@ -51,7 +51,7 @@ public:
 protected:
 	void close ();
 	samplecnt_t read_unlocked (Sample *dst, samplepos_t start, samplecnt_t cnt) const;
-	samplecnt_t write_unlocked (Sample */*dst*/, samplecnt_t /*cnt*/) { return 0; }
+	samplecnt_t write_unlocked (Sample const */*src*/, samplecnt_t /*cnt*/) { return 0; }
 
 	int read_peaks_with_fpp (PeakData *peaks, samplecnt_t npeaks, samplepos_t /*start*/, samplecnt_t /*cnt*/,
 				 double /*samples_per_unit*/, samplecnt_t /*fpp*/) const {
diff --git a/libs/ardour/audio_playlist_source.cc b/libs/ardour/audio_playlist_source.cc
index 08676a4cf9..e832dd2db3 100644
--- a/libs/ardour/audio_playlist_source.cc
+++ b/libs/ardour/audio_playlist_source.cc
@@ -151,7 +151,7 @@ AudioPlaylistSource::read_unlocked (Sample* dst, samplepos_t start, samplecnt_t
 }
 
 samplecnt_t
-AudioPlaylistSource::write_unlocked (Sample *, samplecnt_t)
+AudioPlaylistSource::write_unlocked (Sample const *, samplecnt_t)
 {
 	fatal << string_compose (_("programming error: %1"), "AudioPlaylistSource::write() called - should be impossible") << endmsg;
 	abort(); /*NOTREACHED*/
diff --git a/libs/ardour/audiosource.cc b/libs/ardour/audiosource.cc
index 20f9eeaabf..e65b2eecac 100644
--- a/libs/ardour/audiosource.cc
+++ b/libs/ardour/audiosource.cc
@@ -327,12 +327,12 @@ AudioSource::read (Sample *dst, samplepos_t start, samplecnt_t cnt, int /*channe
 }
 
 samplecnt_t
-AudioSource::write (Sample *dst, samplecnt_t cnt)
+AudioSource::write (Sample const * src, samplecnt_t cnt)
 {
 	WriterLock lm (_lock);
 	/* any write makes the file not removable */
 	_flags = Flag (_flags & ~Removable);
-	return write_unlocked (dst, cnt);
+	return write_unlocked (src, cnt);
 }
 
 int
@@ -918,14 +918,14 @@ AudioSource::done_with_peakfile_writes (bool done)
  * process. _lock MUST be held by caller.
 */
 int
-AudioSource::compute_and_write_peaks (Sample* buf, samplecnt_t first_sample, samplecnt_t cnt,
+AudioSource::compute_and_write_peaks (Sample const * buf, samplecnt_t first_sample, samplecnt_t cnt,
 				      bool force, bool intermediate_peaks_ready)
 {
 	return compute_and_write_peaks (buf, first_sample, cnt, force, intermediate_peaks_ready, _FPP);
 }
 
 int
-AudioSource::compute_and_write_peaks (Sample* buf, samplecnt_t first_sample, samplecnt_t cnt,
+AudioSource::compute_and_write_peaks (Sample const * buf, samplecnt_t first_sample, samplecnt_t cnt,
 				      bool force, bool intermediate_peaks_ready, samplecnt_t fpp)
 {
 	samplecnt_t to_do;
diff --git a/libs/ardour/sndfilesource.cc b/libs/ardour/sndfilesource.cc
index f462b141a2..42dba9d36e 100644
--- a/libs/ardour/sndfilesource.cc
+++ b/libs/ardour/sndfilesource.cc
@@ -599,7 +599,7 @@ SndFileSource::read_unlocked (Sample *dst, samplepos_t start, samplecnt_t cnt) c
 }
 
 samplecnt_t
-SndFileSource::write_unlocked (Sample *data, samplecnt_t cnt)
+SndFileSource::write_unlocked (Sample const * data, samplecnt_t cnt)
 {
         if (open()) {
                 return 0; // failure
@@ -609,7 +609,7 @@ SndFileSource::write_unlocked (Sample *data, samplecnt_t cnt)
 }
 
 samplecnt_t
-SndFileSource::nondestructive_write_unlocked (Sample *data, samplecnt_t cnt)
+SndFileSource::nondestructive_write_unlocked (Sample const * data, samplecnt_t cnt)
 {
 	if (!writable()) {
 		warning << string_compose (_("attempt to write a non-writable audio file source (%1)"), _path) << endmsg;
@@ -736,7 +736,7 @@ SndFileSource::set_header_natural_position ()
 }
 
 samplecnt_t
-SndFileSource::write_float (Sample* data, samplepos_t sample_pos, samplecnt_t cnt)
+SndFileSource::write_float (Sample const * data, samplepos_t sample_pos, samplecnt_t cnt)
 {
 	if ((_info.format & SF_FORMAT_TYPEMASK ) == SF_FORMAT_FLAC) {
 		assert (_length == sample_pos);